Jacoby Ellsbury (sore ribs, ERD 4/21)
Mike Cameron (abdominal pain, TBD)

Injury stacks are one of those concepts that makes so much sense to me and a few hardcore medheads, but has never gotten much traction in the broader baseball world the way that things like cascades or workload increases have, for right or wrong. It's neat that concepts we introduce here make it out into the lexicon and the thinking of baseball. It's not just with fans—Andy MacPhail, who's admittedly old school but has a statistical analyst on his staff, talked about some advanced concepts the other night. (It also reminds me that "interactionism," a term from this brilliant book is one that you're going to be hearing about a lot in coming years.) Anyway, the Red Sox have a stack right now, and while neither injury is serious, it shows how depth can be challenged, especially in a day where some teams are carrying 13 pitchers and have almost no extra guys with gloves. One reason is that teams have learned that depth is a phone call and a flight away in the minor leagues, using that to their advantage, in essence expanding their rosters. Ellsbury is hoping to return Friday, but his ribs haven't made much progress. He was held out on Thursday when he was having pain with breathing. That's not a good sign, but this is one of those injuries that's painful until it isn't. There's not much the medical staff can do but wait for it to heal up. The situation is tougher with Cameron. He exhibited signs of appendicitis and was checked on Thursday. Late word is that Cameron does not have appendicitis and is headed back to Boston where he'll see team doctors to try to figure out what the issue is and how much time he'll miss. (Nick Cafardo called it an abdominal strain, according to Boston radio reports.)

Daisuke Matsuzaka (shoulder, ERD 4/28)
Eleven scoreless innings sounds nice, but when it comes to rehab assignments, the line really doesn't matter. What does is how he got there, and for Matsuzaka, there's some bad mixed in with the good. In both starts, he didn't have plus velocity, living around 90 mph. There's some suggestion that he's not going full-out, pitching to the level of his competition. It didn't go up in the second start, so that's something to key on. His efficiency wasn't great, but never is, so that's not really a worry. He made his pitches, showed some control and command, and was effective. While Matsuzaka says he's ready now, it's more likely he'll get to work with Rich Sauveur for one more start while Boston not only gets one more look at Matsuzaka, but figures out how to sort out their roster. Matsuzaka's return isn't going to just affect their pitching staff.

Lance Berkman (knee, ERD 4/21)
The ERD has moved up for Berkman because there's been some progress. He was able to run lightly without having "significant" swelling afterwards, leading the Astros to schedule a weekend rehab assignment for him. If he makes it through that, they'll put him back in the lineup quickly. The clear path back is good news for Berkman and the Astros, but for the medical staff the work isn't close to over. Assuming that Berkman does everything he's supposed to without a recurrence of the swelling, there's going to be a lot of maintenance work for them keeping Berkman in that state. The swelling and pain will have to be handled, plus they'll have to work closely with Brad Mills to make sure that Berkman gets the proper rest. We can safely assume that Berkman will get some extra time off, such as day games after night games, but there's no real way to put a solid expectation on playing time or production. The two will definitely go hand in hand, but rely completely on keeping Berkman's knee healthy, something that's been tough so far.

Edwin Encarnacion (right arm soreness, 4/19)
The Jays will be without Encarnacion for a few days and they're being a bit cagy about why that's the case. Encarnacion has struggled after injuring his wrist last season, so that's an immediate concern when the team lists "right arm" as the issue. MLB's Jordan Bastian says it's not the wrist, but sources are very vague on what the problem actually is. If this is just soreness and fatigue after an abbreviated camp, he'll miss a couple days. The worry is that there's something more, perhaps some kind of cascade going on, and that could cost him more time. Encarnacion has made some strong throws, so weakness doesn't appear to be an issue, making me think that the stamina issue is the most likely reason. The Jays' staff is making a smart move here.

Brian Roberts (abdominal strain/herniated disc, ERD 5/14)
Yes, what I was worried about with Roberts went beyond that worry and all the way to the worst-case scenario. By that, I mean I was worried that the abdominal strain might be related to his previous herniated disc. No, it actually was an exacerbation. Tighten your abdominals and you'll feel yourself "sit up" as your posture gets better. The abdominals and spinal erectors work together, along with the skeleton to keep us upright and they need to be in balance. Roberts obviously has weaknesses there, and the two concurrent injuries are really acting against each other. Not only is there the pain-spasm cycle, but there are really two associated ones. The Orioles are acknowledging that Roberts will be out longer than the minimum; he'll be out until mid-May, with a real chance that this lingers on.

Mike Gonzalez (strained shoulder, 4/25)
Koji Uehara (strained hamstring, 4/30)

Since I spent the last few days in the Baltimore/DC area, catching three games at Camden Yards, forgive me if I'm a bit more concerned with the O's than most. (Given the crowds over the three-game sweep, I might be one of very few.) It's flat out a mess in the O's bullpen right now, and it seems like Dave Trembley has lost them, if not the whole clubhouse. The tension is palpable there, and many think that Trembley might not be long for the job. His handling of the Gonzalez situation, throwing him under the bus so quickly and then questioning his DL move, is a real puzzler. Gonzalez's "mechanical work" is something that could have been taken care of in camp if Trembley's handling of the vets in camp hadn't been so lax. Now that they need to DL him, the shoulder strain is enough to pass muster and fill in the slot after Trembley burned through the pen willy-nilly. It's one thing to lose a closer, and another thing to completely lose touch with a pen's strengths and weaknesses. Gonzalez's stint likely won't be too long. He was scheduled to come back to the pen early next week after working on the side, so assume that it should be about the minimum. If there's any positive, it's that Uehara is throwing and looking like he'll be ready to get back to the pen by late April. His presence could work a lot of ways. He could be a smoothing option for the long role or slot into the closer role, since Trembley seems to have more confidence in him than Gonzalez.

Brad Lidge (elbow, 4/28)
The Phillies might be getting Lidge back a little sooner than expected. Lidge is going to make a couple more rehab starts on Saturday and Monday and if all goes well there, they'll go back to back with him later next week. That will really be the final test before coming back to Philly. They don't need him to close, though that's obviously where Charlie Manuel expects to use him quickly. Lidge still isn't at his normal velocity, but reports from Clearwater are that his slider is biting and he's got enough on his fastball to work with. They expect there's a little more there than the 90-91 mph that he's been topping out at. Given his lack of work and the physical problems, that's a reasonable assumption. The Phillies aren't going to rush him back, but things are beginning to clear up in figuring out just what Lidge might look like when he gets back.

Carlos Zambrano (wrist)
Someone texted me to ask what I thought about Zambrano's 123-pitch outing. I replied "big deal." Of course, when he told me that Zambrano had racked up 123 pitches in just five innings, my opinion changed a bit. Twenty-five pitches per inning is simply outrageous. In fact, some organizations have a 30-pitch rule, where a pitcher is pulled if he hits 30 pitches in any inning. While the final line wasn't all that terrible, the big issue appears to be cramping in Zambrano's wrist, a problem that he's had before. I'm sure many Cubs fans recall the "chatting with his brother" issue from a couple seasons back, so I guess we'll have to look into that excuse. That issue cleared up before and if that's at the root of his inefficiency, it's not a long-term concern. Zambrano is expected to make his next start on schedule.

Scott Kazmir (shoulder weakness)
There's not much to be positive about in Kazmir's first start of the 2010 season. He didn't show much of anything, besides a gopher ball that he normally doesn't feature. The velocity was there, and I'd be curious if the PitchF/X gurus saw anything different in his movement. The upside here is that he was healthy, making pitches, and didn't seem to have any physical issues besides perhaps stamina, which he didn't stick around long enough to test. It wasn't a shoulder problem or any other physical ailment, as it so often is. Instead, this looked like nothing more than rust. Kazmir is a pitcher whose mechanics can come and go, so expecting him to come out and dominate was unlikely. Now, the Angels will need to go back to work with Kazmir on the side and see if they can find that space for him where he's at least good, if not the strikeout king they thought they were getting last season.

Quick Cuts: There's a reason that the term "flu-like symptoms" is a catchall for baseball illnesses. Sometimes too much honesty is, well, way too much. … There's been no progress for Ian Kinsler. I wish I had more, but there's really nothing to this besides waiting for the ankle to heal. … Here's a really interesting story on Jose Guillen's injuries late last season. … Jayson Werth was back in the lineup last night. He wasn't running at 100 percent, but it looks like his hip flexor strain isn't that serious. … C.J. Wilson missed his Thursday start due to food poisoning. He'll slot back into the rotation as soon as possible. … Pat Neshek is having an issue with a finger on his pitching hand. It doesn't sound too serious at this stage, but finger injuries can be very problematic for pitchers. … Word out of Minnesota is that Jose Morales is "way behind schedule. The train's not moving." In other words, his wrist injury isn't making much progress after surgery and he could be out longer than mid-May unless there's a breakthrough. … Late word from Baltimore on Felix Pie. He injured his shoulder on a swing. It is the left shoulder, which has been an issue before. … Thank me later. … I'll be down in Louisville on Friday evening to see Aroldis Chapman. Expect a report here soon.