When Oswaldo Arcia caught a fly ball, wound up and threw it home in the fourth inning Sunday, he successfully prevented White Sox baserunner Alexi Ramirez from tagging up and trying to score.

Arcia also sidelined himself for at least the next two weeks.

Arcia winced as he made that throw, feeling pain in his hip. And when he batted in the bottom of the inning, the pain got worse. He lined a single into right field, and “I hit the ball hard, and went, ‘Ohhh!’ ” the Twins outfielder said Monday. He limped to first base and was removed from the game; a day later, a magnetic resonance imaging test found a strain in the right flexor muscle in his hip.

The 23-year-old Venezuelan was placed on the 15-day disabled list shortly afterward, and Eddie Rosario was called up from Class AAA Rochester to replace him.

Arcia insisted that his injury isn’t serious and that he won’t need two weeks to recover — “If I keep working, I can play,” he said — but manager Paul Molitor was unwilling to play shorthanded for a week.

“You try to give the player the benefit of the doubt, but after the testing today, the trainers [and] doctors report [that] it’s going to be at least that,” Molitor said. “You can’t hamstring yourself for that length of time. You also don’t want to give the player the opportunity to make a decision to get out there too soon, and this kind of insures he won’t do that.”

Molitor said he could tell that Arcia wasn’t right after the throw.

“I kind of regret, maybe, somewhat, that I didn’t get him out of that game earlier. He kept telling me he’s fine, he looked like he was fine,” Molitor said. “Then that last at-bat, it looked like it grabbed him pretty good.”

The Pelfrey riddle

Twins General Manager Terry Ryan said Monday that the Twins have “a mystery to solve,” that being: What happened to Mike Pelfrey?

After giving up only one run over 14 innings in his two previous starts, the righthander endured a bizarre fourth inning with a 7-0 lead against the White Sox on Sunday, losing control of his pitches so badly, he had to be removed. He walked a batter, gave up a single and hit three batters, two of them with the bases loaded. “And it came out of nowhere,” Ryan said. “All of a sudden, [his control] just went. It went quick. So either mechanically or mentally, something happened.”

The solution is to “get back into the flow of the game,” the Twins general manager said, but “it’s hard. … He slowed the game way down, took too much time between pitches, didn’t get on the mound. Some of the stuff we’ve talked about before.”

Ryan said he was impressed Pelfrey made no excuses for his problems, but “we’ll just have to solve that mystery. He’s going to get the ball here in four more days.”

Etc.

• Outfielder Aaron Hicks and catcher Josmil Pinto weren’t recalled to take Arcia’s spot, but Molitor said the team’s reports on the two players at Class AAA Rochester have been positive. “Aaron’s doing fine, I’m hearing some really good things about him,” Molitor said. “It’s important for him to know that he needs to continue to do that over a little bit longer period of time. His day could come soon as well.”

• To fill Rosario’s spot at Rochester, the Red Wings activated former Twins outfielder Wilkin Ramirez from the seven-day disabled list.