By the time the Twins play the White Sox on Friday, their roster could look a little different.

Outfielder Josh Willingham is expected to join Class AAA Rochester on Monday to begin a rehabilitation assignment. Willingham, who will play with a brace on his surgically repaired left knee, will be the designated hitter for one or two days before playing in the outfield. But Willingham was running well — as well as can be expected for him — during workouts at Target Field. The Twins would like to have Willingham back in time for Friday's doubleheader in Chicago.

Outfielder Darin Mastroianni will leave Class A Fort Myers Tuesday and join Rochester as well. It's just as important for Mastroianni to join the Twins as Willingham. Willingham will give them the power presence they need in the middle of the lineup. Mastroianni will give them a second possible center fielder.

If something happens to Clete Thomas before Mastroianni is ready, the Twins might have to play Oswaldo Arcia in center. Arcia has played 77 minor league games in center but is more suited to be a corner outfielder.

Outfielder Wilkin Ramirez joined Class AA New Britain as he continues his rehab assignment and could emerge as an option.

There will be fallout from these moves. Mastroianni, for instance, is on the 60-day disabled list and has to be added back to the 40-man roster. That means someone must come off.

Willingham will deepen the lineup, but someone will lose at-bats, and it could be Ryan Doumit.

"Chi-Town will be decision time, it seems to me," manager Ron Gardenhire said.

Also, with a doubleheader Friday, the Twins, per league rules, can call up an extra player for the day. Righthander Liam Hendriks is a strong possibility, although he lost Sunday for Rochester.

No waivers for Mauer

The Twins learned their lesson. Assistant General Manager Rob Antony on Sunday said the club has no intentions of placing All-Star catcher Joe Mauer on waivers because "there was just too much confusion."

Antony revealed the change in approach during a conversation about the overall waiver process. The Twin Cities was on high alert last August when it was learned that Mauer and his $23 million annual salary had been placed on waivers. The Twins had no intentions of trading him — they had placed Kirby Puckett and Paul Molitor on waivers in the past.

"Last year we ran everybody through, and everyone got into a panic because they found out Joe Mauer was on trade waivers," Antony said.

Still, the waiver flap ruined the announcement that the All-Star Game was coming to Target Field in 2014 because everyone had questions about Mauer.

There will be no such flap this year. GM Terry Ryan said on Wednesday that he plans to run about 20 players through waivers this month.

PED-Day?

According to reports, Major League Baseball is prepared to announce which players, in addition to the Yankees' Alex Rodriguez, will be suspended as part of the Biogenesis scandal. There are no indications any Twins will be suspended, but Gardenhire just wants to move away from the latest drug scandal.

"I don't have any opinions on it," he said, "because it's not my job and I don't have to get involved, so I'm not going to get involved. This is not the best moment in baseball when we are dealing with this stuff again."