The A's have made a real habit of sudden roster moves that tend to surprise (and disappoint?) fans this year, and they continued that trend on Wednesday. Kila Ka'aihue, in whom many fans had placed their faith at first base given Daric Barton's continued struggles, was designated for assignment, and Brandon Moss was added to the 40-man roster and called up.

Ka'aihue hadn't hit this year, batting just .234/.295/.398, which is poor even in the Coliseum, and for a first baseman to hit that is unacceptable. Of course, it was just 139 PAs, but he's now got 465 PAs in his career with a line almost identical to his 2012 figures. Maybe he can still pull it together -- stranger things have happened. But the A's have a younger Barton, a younger Chris Carter, and, most relevantly, a similarly-aged Brandon Moss all available to them, so there's no real reason to keep giving chances to someone with a low probability of progressing beyond mediocrity.

Moss has spent the season ripping up the PCL, batting .286/.371/.582, which works out to a .314 TAv and follows the .311 TAv he posted in the International League last season. On the other hand, he's got 749 PAs in the majors and just a .232 TAv. PECOTA has him down for a .262 TAv, mainly because guys who hit as well as Moss has in AAA aren't supposed to be Jamey Carroll when they reach the majors. Of course, .262 isn't anything special for first base, so it's not like Moss, who's 28, is likely the sudden savior at first, a hidden gem just waiting for his chance to shine. He's a guy.

Given this basic guy-ness, one does wonder why the A's wouldn't take the opportunity to give Chris Carter some more at-bats. He's already on the 40-man, he's an actual prospect, and he hit well at AAA last year. On the other hand, he hasn't really done much in Sacramento this season, and his defense is something to write home about in the sense that when you get into a car accident, you tend to write and tell your parents that it happened. (Moss, though, is an outfielder learning the position, so how much better can he be?)

I don't have an answer to this. I've seen speculation that Moss is only up for a few games, filling the slot until the A's call Daric Barton back up, and that they don't want to give Carter a three-game trial. If you're going to disrupt someone's routine, you do it to the 28-year-old journeyman, not the guy who might still be a contributor if he can develop in a few key areas. I'm not entirely convinced that the factual premise here is correct, but there's not really too much point arguing about it now, because we'll know in a few days.

At the fringes of the bullpen, Andrew Carignan apparently hurt his elbow, and it might be serious. Evan Scribner, who was one of the last A's cuts in spring training, was added to the 40-man roster (the A's had an empty slot because they waived Neil Wagner last week) and called up. Scribner has pitched quite well at Sacramento, with the only warning flag being an elevated homer rate, but the PCL has been known to play tricks. The strikeouts are there and the walks are low. Scribner won't pitch in any situations that matter (just like Carignan wasn't), but I'm hopeful that he gets a few chances soon so we can get a real, non-spring-training look at his pitches and approach.