"I wish I could keep hitting with my broken rib, but unfortunately it's getting worse and worse," Plouffe said. "I guess it's a symptom of it where the first couple days I was able to play through it, but then yesterday and the day before it was pretty painful. So we decided to get an MRI and see what was going on in there. And there was a fracture."
Plouffe underwent the MRI exam on Sunday, and the Twins received the results later that night. Plouffe said it's been a frustrating year on the injury front, as he also missed 13 games in late April with a strained right intercostal. He's been dealing with a strained groin recently as well, and said he's been playing at about 65-70 percent this year.
"I've had a lot of stuff all year," Plouffe said. "It's been tough. I've had injuries before, but not where it's plagued me throughout a year. At least this will give a chance for the rest of my body to catch up. You have to find a silver lining."
With Plouffe expected to be out at least four weeks, it also means there's very little chance he'll be traded before the Trade Deadline on Aug. 1. Plouffe, who is under team control next season as well, could still be part of an August waiver trade, but this injury makes it more unlikely.
"I don't know what's going to happen with that now," Plouffe said. "I guess I never knew."
With Eduardo Escobar dealing with a strained left hamstring and Byron Buxton out the last two games after running into the center-field wall on Saturday, Minnesota went with bringing up a position player in Vargas instead of activating reliever Trevor May from the 15-day disabled list.
Vargas was hitting .235/.353/.435 with 14 homers, 13 doubles and 53 RBIs in 82 games with Triple-A Rochester. It's the first time he's been called up this year, and he started at first base and batted fifth against the A's on Monday.
"Given where I feel we needed to add support in the short-term, his bat made more sense than a guy like [middle infielder Jorge] Polanco," Twins manager Paul Molitor said. "He gives me some flexibility at first base with Joe [Mauer] and at DH with Miguel."
Rhett Bollinger has covered the Twins for MLB.com since 2011. Read his blog, Bollinger Beat, follow him on Twitter @RhettBollinger and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.