CLEVELAND -- If Tigers officials are waiting for top prospect Nick Castellanos to cool off from his hot start to see how he adjusts to pitchers, they might be waiting a while. The sweet-hitting third baseman at Class A Lakeland raised his average to .413 entering play on Thursday thanks to an 8-for-12 tear over the previous three games.

The 20-year-old went 4-for-4 on Tuesday night at Bradenton, sandwiched between a pair of two-hit efforts. He easily leads all Minor League hitters across all organizations in batting average.

The plan going into the season was for Castellanos to spend the summer at Lakeland with a promotion to Double-A Erie no earlier than the tail end of the season. He said a few weeks ago that he isn't trying to think about assignments or levels and instead is just concentrating on his hitting.

Tigers send Jackson to disabled list

CLEVELAND -- Decision time has come in regard to Austin Jackson, and it isn't good news. The Tigers have placed him on the 15-day disabled list, retroactive to May 17, with the abdominal strain that has sidelined him for more than a week and left the club a man short just as long.

Jackson was sent home to Detroit for tests, including an MRI, as well as examination by team doctors following Thursday's 2-1 loss to the Indians.

The Tigers had pushed back the decision by purchasing Quintin Berry's contract, but they had an unofficial deadline of Friday, when Ryan Raburn returns from the bereavement list for the series opener in Minnesota.

The extra time didn't help. Jackson didn't do any activity the past two days after feeling pain taking swings in batting practice on Tuesday night.

"It's somewhat getting better," Jackson said after Thursday's loss, "but it's still a little bit away from where it needs to be."

Raburn will take Jackson's place on the 25-man roster.

Teams can backdate a player's placement on the DL up to 10 days, and Thursday marked the eighth day since Jackson strained the abdominal muscle on a swing. He'll be eligible to return in time for the start of the next homestand, on June 1 against the Yankees.

Manager Jim Leyland does not like to discuss the impact of injuries, fearing it sends the wrong message to a team that has to overcome them. Still, he isn't downplaying this one.

"Everybody's making moves, everybody's got guys on the DL," Leyland said. "Jackson's [injury] is the one that hurts [us]."

Avila being approached differently in 2012

CLEVELAND -- The Tigers aren't far off from the pace from this point last season, but some individual players are. One of them is Alex Avila, who seems to be getting a different approach from opposing pitchers compared with his breakout 2011 campaign.

An American League scout who follows the Tigers noted that Avila is getting far fewer fastballs to hit than last season, and the stats bear that out. According to fangraphs.com, Avila saw fastballs with 57.2 percent of the pitches thrown to him in 2011, just slightly under his previous averages in Detroit. By contrast, just 51.8 percent of pitches to him have been fastballs so far. A look at pitch f/x and four-seam fastballs on fangraphs.com shows that the difference is even greater, from 37.4 percent in 2011 to 28 percent this season.

Instead, Avlia is seeing more curveballs and changeups, with a few more cutters mixed in. On Wednesday, Indians reliever Vinny Pestano used a slider to start Avila's pitch-hitting appearance, then went back to sliders to set up a fastball on the outside corner for a called third strike.

Avila hit .327 off fastballs last year, according to data from STATS. He's hitting .328 off them so far this season. However, he's hitting under .200 against everything else, with no hits yet off changeups. He batted .383 off changeups last year, according to STATS.

Avila entered Thursday's series finale with a .222 average, 61 points below his average at this point through last season, with 34 strikeouts through 138 plate appearances. Manager Jim Leyland believes that Avila will come around, but he doesn't want to see his All-Star catcher fall into a tentative approach.

"I just think he needs to stay aggressive," Leyland said. "He'll do fine."

Tigers activate Marte, strengthening bullpen

CLEVELAND -- Luis Marte made the Tigers' bullpen out of camp, only to strain his left hamstring pitching in the final game of Spring Training. Now he'll finally get his shot to pitch for the big league club

The Tigers activated the high-strikeout right-hander after Thursday's game, bringing their bullpen just about back to full strength.

The move had been expected once Marte came out of Monday's rehab appearance for Triple-A Toledo feeling fine, having tossed three scoreless innings with one hit with two strikeouts. Detroit delayed the move only to rest him long enough to be able to pitch once they finally activated him.

Marte pitched in four games for Detroit last year as a September callup, allowing one run on six hits with three strikeouts over 3 2/3 innings. His Spring Training performance, however, more closely resembled last year's at Double-A Erie, where he struck out 68 over 53 innings with a 1.70 ERA.

To make room on the 25-man roster, the Tigers optioned right-hander Luke Putkonen to Toledo. The 26-year-old gave up seven runs on 14 hits over 7 1/3 innings with five walks and six strikeouts.