Twins lefthander Hector Santiago wonders if pitching in the World Baseball Classic is the reason why he has landed on the disabled list for the first time in his seven-year big-league career.

He pitched 8â…” innings for Puerto Rico as it reached the tournament final before losing to the United States. It required him to start throwing earlier than normal, as well as pitch in meaningful games while others eased their way through spring training.

"It was the first time I started that early, and the first time I've been on the DL," said Santiago, who was 1-0 with a 2.08 ERA during the WBC.

The Mets' Seth Lugo, a fellow Puerto Rican, landed on the DL after the WBC because of a partly torn ulnar collateral ligament. Kansas City's Danny Duffy, who pitched for Team USA, had to be put on the DL last month because of a strained oblique. And Seattle ace Felix Hernandez, who pitched for Venezuela, is on the DL because of bursitis in his right shoulder.

Santiago went on the DL on June 7 because of shoulder soreness. A day earlier, his velocity was down and his command was off as he lasted only 2â…” innings. His velocity, actually, is down 2 miles per hour since April, from 91.5 to 89.4 mph, which might have played in the Twins' decision to send him to the trainer's room.

After a few days of shoulder strengthening work, Santiago said he feels good. He has played catch back-to-back days and is scheduled for long toss drills Tuesday. He holds out hope he can be ready to pitch once his 10 days are up, meaning he could start in one of Saturday's two games against Cleveland.

"I just think it is something that has happened over time, from throwing in the WBC, throwing that early," he said.

Polanco returns, sits

Jorge Polanco returned from the bereavement list after being out since June 3 for the death of his grandfather in the Dominican Republic. But Twins manager Paul Molitor opted to ease his shortstop back into things, keeping him out of Monday's starting lineup.

To make room on the 25-man roster for Polanco, the Twins sent righthander Chris Heston to Class AAA Rochester. He made his Twins debut Sunday, pitching one inning at San Francisco, after being claimed off waivers last week from the Dodgers.

Kennys Vargas stayed with the Twins, even though that meant cutting back to 12 pitchers. He started at designated hitter in Monday's 14-3 loss to the Mariners.

"When [Vargas] gets in there, he's got a chance to impact the game," Molitor said.

Answers elude Hughes

The Twins still have no timetable for righthander Phil Hughes' return from his right shoulder injury. Molitor said Hughes has experienced "sensations in fingers and things that we're not totally sure what the source is."

"We're going to try to do the best we can to try to get to the bottom of what we need to do to get him moving forward," Molitor said. "Try to get him to throw a little bit and address those things, but we're still not sure the best way to go."

Etc.

• The Twins sent reliever Alex Wimmers back to Class AAA Rochester following Monday's loss with plans to announce who's replacing him Tuesday. Wimmers has posted a 4.76 ERA in five appearances with the Twins.

• Injured three-time All-Star lefthander Glen Perkins (shoulder) is scheduled to pitch a simulated game Tuesday in Fort Myers, Fla. "Potentially if things go well, he's going to join the [Class A] Miracle here [on a rehab assignment] in the next 10 days or so," Molitor said.

• The Twins signed reliever Tim Melville, 27, and assigned him to Rochester. A fourth-round pick of the Royals in 2008, he has nine innings of MLB experience with the Reds in 2016. He was 3-4 with a 3.45 ERA for Long Island of the independent Atlantic League when the Twins signed him.