A magnetic resonance imaging exam of top prospect Byron Buxton's left wrist has revealed an aggravation of the same sprain he suffered in March, meaning the young outfielder will be out indefinitely.

Buxton flew to the Twin Cities to undergo the MRI and be examined by Twins hand specialist Dr. Tom Varecka. He will return to Fort Myers, Fla., and work out at the extended spring training facility until he can play in games again.

The problem: No one knows when he'll be able to play. While attempting to make a diving catch March 16 during a minor league spring training game, Buxton sprained the pisotriquetral joint in the wrist. The Twins were told it can be a slow-healing joint, and it was — Buxton didn't play for Class A Fort Myers until May 4. A similar delay could knock Buxton out until July.

Buxton, 20, was the consensus top prospect in baseball heading into the season and scheduled to start the season at Class AA New Britain. He was 3-for-20 in five games at Fort Myers before reinjuring his wrist. Now he could miss at least two months of games. That's missed development time.

"It's always disappointing," Twins assistant general manager Rob Antony said. "It's disappointing that [third baseman prospect Miguel] Sano is missing the season [rehabbing after Tommy John surgery] as well. Now Buxton. Losing out on development time is a big thing."

Wall padding problem

Aaron Hicks and Sam Fuld: Both are center fielders. Both have had concussions this season. Both hit their heads about the same place on the center field wall at Target Field to trigger their injuries.

See where this is headed?

Both said Tuesday that Target Field has one of the harder walls in baseball and want more padding on it.

Fuld hit the wall May 2 while robbing Baltimore's Manny Machado of a hit, but the symptoms didn't appear until the morning of May 8 when the team was in Cleveland. He said he finally feels better.

Hicks hit the wall May 1 while chasing a ball against the Dodgers.

"It's definitely one of the harder walls," Hicks said. "You can tell by the way it comes off the wall when guys hit doubles and stuff. It shouldn't kick back that much."

Little did they know the Twins already were looking into the issue, led by owner Jim Pohlad.

Antony said he received a phone call from Pohlad after Fuld was diagnosed and asked if there was anything the club could do to make that area safer.

"We actually have talked about it," Antony said. "We're looking to see if there are any options of outfield walls we could install. I have to check with Major League Baseball to see if it's something we could do during the season or after the season."

Etc.

• Outfielder Josh Willingham took early batting practice and is getting closer to playing. He hasn't played since April 6 when he suffered a small fracture in his left wrist when he was hit by a pitch in Cleveland.

• Reliever Casey Fien said he has full range of motion in his right arm after being hit near the biceps by a Victor Martinez line drive Sunday and was prepared to pitch as needed.

Joe Mauer returned to first base for the first time since May 4, when back spasms forced him out of a game against Baltimore. He battled lower back pain after that, missing five games. He was the designated hitter in the final two games of the weekend series in Detroit.