Righthander Nick Burdi, the hardest thrower in the Twins organization, has a torn ulnar collateral ligament and will have season-ending Tommy John elbow ligament replacement surgery.

Burdi, with Class AA Chattanooga, pitched a scoreless 1⅓ innings Sunday vs. Biloxi but gave up three hits — he had allowed six all season before that — and lowered his ERA to 0.53.

“He had some pain in his elbow after his last outing,” said Derek Falvey, Twins chief baseball officer. “A precursor to some of the issues with a UCL, so we had him seen, brought him up here to Minnesota and had him evaluated.”

The exam revealed a torn ligament, so the club is working to schedule a time for surgery.

It’s a huge blow for Burdi, who was trying to get back on track after pitching only three innings last season because of a bruised humerus. He was on track to be promoted to Class AAA.

It’s also a blow to the Twins. Burdi’s fastball is around 98 miles per hour and has hit 100 a few times this season.

“We all feel terrible,” Chattanooga manager Jake Mauer said. “He was throwing the ball very well. It is very disappointing.”

Perkins ready for more

Veteran lefthander Glen Perkins threw in the bullpen Friday, and the session went very well. He used all of his pitches as he threw close to maximum effort.

It’s a significant sign that he has cleared a big hurdle in his return from shoulder surgery last year.

“He’s gotten to a point to where he feels really good,” Falvey said. “He has been more aggressive in his throwing program. When you have this type of surgery, you want to be more attentive to the details as you are bringing him back and don’t want any setbacks.”

Perkins will throw one more time on Tuesday, possibly facing hitters, before heading to Fort Myers to pitch in extended spring training games.

Perkins pitched in just two games last season before landing on the disabled list on April 13 because of shoulder problems. He then had surgery June 23 to repair a torn labrum, a surgery in which the labrum had to be re-attached to the bone.

Falvey would not speculate on how much time in the minors Perkins will need before returning to the Twins, but he’s clearly reached the point where the next phase of his comeback can take place.

“You don’t want to put a guy in front of hitters if they aren’t there yet,” Falvey said. “He’s pretty close.”

Hughes seeks answers

Righthander Phil Hughes will have a second opinion on his ailing right shoulder as he investigates the source of his problems.

In his latest test, his shoulder was checked for a possible nerve problem but the test came back clean. After being examined by Twins doctors, Hughes is looking for a specialist to take a look at his case.

“Trying to get to the bottom of this,” he said.

Hughes felt discomfort during his start Sunday against Kansas City and felt it was similar to what he had gone through when he needed surgery to treat thoracic outlet syndrome.

“We are very likely to explore another opinion and get into some detail with respect to his thoracic issue in the past to figure out if there’s some elements to what occurred last year,” Falvey said.

Etc.

• Lefthander Adalberto Mejia arrived in town as he prepares to start Saturday. He last pitched Sunday in the second game of a doubleheader against the Royals as the 26th man. He had to return to Class AAA Rochester, where he threw in the bullpen Wednesday.

• The Twins designated lefthander Adam Wilk for assignment to make room for Mejia. Wilk was 0-0 with a 3.86 ERA in two outings.