DETROIT -- Doug Fister threw approximately 50 pitches Thursday morning in his first mound session in over a week, a positive sign that he isn't far off from pitching again. Still, he isn't close to helping the Tigers quite yet, and almost certainly not close enough to fill the open rotation spot coming up Monday, which the Tigers have not decided how to fill.

Fister told coaches he felt good throwing. If his arm feels fine Friday, he'll likely be scheduled for another mound session over the weekend in New York. At that point, he'll have been sidelined for three weeks since straining a muscle around his rib cage during his season-opening start. Add in the time he lost in Spring Training with a sore right middle finger, and Fister has pitched in just two games over the past five-plus weeks.

"I don't know how many times you'd have to throw before you go out for a rehab start or face hitters here. I don't know," manager Jim Leyland said. "I don't have the answer. When I get it, I'll give it to you. I'm certainly looking forward to his return, but right now I don't have any information for you."

Add up the signs, and the Tigers will need a replacement for Fister for at least one more turn through the rotation, and probably two. They have to decide whether to move Duane Below in from the bullpen or call up another starter from the Toledo Mud Hens, such as Casey Crosby or Andy Oliver. Both had quality starts in their last outings.

Eldred to immediately fill DH slot

DETROIT -- When Brad Eldred signed a Minor League deal with the Tigers over the winter, he was meant to be a veteran bat for the offense ... at Triple-A Toledo.

After three weeks of some of the hottest April hitting seen from a Mud Hen in years, the Tigers are hoping he becomes the spark for an offense that includes Miguel Cabrera and Prince Fielder, but hasn't included many outbursts lately.

In every sense, the 31-year-old Eldred has hit his way into another shot in the big leagues.

"I'm going to run him in there," Leyland said. "He's been one of the hottest hitters in baseball, in the Minor Leagues. I'm DH-ing him and I'm going to put him in that spot. How long depends on how he does."

If he can somehow keep hitting like this, he might be there a while.

Eldred spent 10 Minor League seasons in five different organizations, the first six years in Pittsburgh, with just 282 big league plate appearances to his credit before landing with the Tigers this spring at age 31. With a relatively young everyday lineup, no proven hitters and a history of wrist issues for first-base prospect Ryan Strieby, Eldred gave the Tigers protection, plus maybe a bench bat in case of an injury in Detroit.

The Tigers' lineup is pretty healthy, but the offense is not. Enter Eldred, who hit .388 with 13 home runs and 35 RBIs through 20 games with the Mud Hens. Five of those homers and 10 RBIs came in his last three games, including a three-homer, seven-RBI effort Tuesday night at Columbus. Almost all of those games came as the Hens' designated hitter.

The Tigers have had a rotation going at DH, where seven different players have combined for three RBIs and no home runs. They'll make room for Eldred.

"The guy's doing something right now that everybody's talking about," Leyland said. "I don't know how it's going to play out."

Putkonen replaces Weber in bullpen

DETROIT -- Hours after the Tigers made one roster move to get a fresh arm for the bullpen, they made another one Thursday morning. After Tigers coaches and front-office people met in manager Jim Leyland's office Thursday morning, they announced they were optioning Thad Weber back to Triple-A Toledo.

Taking his place will be right-hander Luke Putkonen, who was not on the 40-man roster. The Tigers purchased his contract, using the spot that opened up when Al Alburquerque was transferred to the 60-day disabled list.

Putkonen came out of the same 2007 First-Year Player Draft that produced Rick Porcello. The right-hander out of UNC had allowed two runs on nine hits over 13 innings this season, walking five and striking out 10.

A strong Spring Training earned Putkonen notice after he went 3-13 last year with a 6.44 ERA combined between Class A Lakeland and Double-A Erie. A full-time conversion to the bullpen not only helped his pitching, but helped his cause in climbing the developmental ladder in a farm system stocked with starting pitching at the upper levels.

"Putkonen's throwing the ball very well," team president/general manager Dave Dombrowski said. "We're anxious to get him here and see. He and [Brayan] Villarreal give us a couple more power arms out in the pen."

Weber was up for four games and pitched in two of them, allowing four runs in as many innings on 10 hits and two walks. His long relief Wednesday left him unable to pitch in Thursday's series finale, and once the Tigers ruled him out of the running to replace Adam Wilk in the rotation, his return to Toledo was sealed.

Math Day reinforces importance of education

DETROIT -- The Tigers hosted their first Math Day event Thursday morning for local schoolkids to get an appreciation of how baseball relies on numbers.

While students sitting behind the visiting dugout watched video presentations from Hall of Famers Andre Dawson and Dave Winfield posting stat questions for them to answer, manager Jim Leyland and third-base coach Gene Lamont were quietly in the other dugout figuring them out themselves. Some were pure stats, such as calculating hit totals based on at-bats and batting average. Others involved angles and distances. It was a good refresher course.

Tigers director of baseball operations Mike Smith was among the speakers, providing examples of how Major League teams use numbers and formulas to evaluate players. He also explained how clubs try to take some of the variables out of their measurements, from small sample sizes early in the season to ballpark factors. As he put it, the stats are only as good as your data.