MINNEAPOLIS -- Just when Joe Mauer was getting on a roll, pain forced an early exit.
Mauer extended his hitting streak to 12 games with a two-run double down the left-field line in the fourth inning, but was noticeably limping as he ran to second base. The team said he has a strained oblique muscle on his right side and will be evaluated Wednesday.
''I've been kind of battling this area for about a week or so, maybe a little more,'' Mauer said. ''I've been stiff and getting it loose and everything's been fine, but today on that one swing, ball down the line, it felt like somebody hit me pretty hard right there.''
Mauer missed almost a week earlier this year with a bad back and sat out the final 39 games last season with concussion-like symptoms.
''I've never had this happen before, so I hope it's a lot sooner than what guys in the past have had,'' Mauer said. ''I've been feeling pretty good and getting some results, so it's bad timing.''
Eric Hosmer had four hits for the Royals.
Ricky Nolasco (5-6) earned his first win in five starts, allowing one run and eight hits in six innings.
Minnesota signed Nolasco to a $49 million, four-year contract in the offseason, hoping he would help a rotation that had a major league-worst 5.26 ERA last year. Nolasco has struggled, however, posting a 5.49 ERA. He pitched more than six innings just once in his past 11 starts.
Twins manager Ron Gardenhire said before the game that Nolasco had a good bullpen session last weekend in hopes of improving his mechanics to get better command of his fastball to set up his breaking pitches.
Nolasco was better Tuesday, but remained far from dominant. He gave up six hits in the first three innings before settling down and retiring the Royals in order in the fourth and sixth.
''I didn't have too many quick innings, but it was just kind of battling and I made some pitches when I had to,'' Nolasco said. ''[My fastball] was better. Just trying not to do too much. It's a step in the right direction.''
Kansas City starter James Shields (8-4) was hoping a new month would change his fortunes. It didn't.
In his shortest outing of the season, Shields allowed nine hits and five runs -- four earned -- in five innings. Although he struck out five, he was constantly behind in the count, leading to a 113-pitch outing. It was his first loss since May 2, a span of 10 starts in which he had five wins and five no-decisions.
The right-hander has a 5.66 ERA in his past eight starts, and only twice has he allowed three or fewer runs.
''I actually thought I made some pretty good pitches and they just found a lot of holes today,'' Shields said. ''It's definitely frustrating that I'm not getting outs. I'm not getting my job done.''
Nunez homered and Sam Fuld had a two-run single as part of a five-run sixth inning for the Twins. Minnesota scored more than five runs for just the third time in 16 games.
''We got some breaks,'' Gardenhire said. ''They always say it evens out, so hopefully this is the start of it evening out.''
A miscue by the Royals gave Minnesota a 2-1 lead in the third.
With Nunez on first, Chris Parmelee hit a popup to short left field with two outs. Mike Moustakas backpedaled from third base as left fielder Alex Gordon was coming in. The two nearly collided and the ball bounced off Gordon's glove to put runners on second and third. Kendrys Morales drove in Nunez with an infield single.
''I think Gordy just thought that he wasn't going to get there, then at the last second realized he had a chance to get there and they both get there at the same time,'' Royals manager Ned Yost said.
An RBI double by Parmelee scored Nunez in the first, but an RBI single by Moustakas evened the score in the second.
Minnesota's Brian Dozier, who has started 79 of 82 games at second base, got the night off. He is in a 1-for-24 slump, and Gardenhire said he could sense some frustration. ... Raul Ibanez started in right field for Kansas City and went 1 for 4. The 42-year-old was signed Monday after being released by the Angels on June 21. ... Twins 3B Trevor Plouffe hit his career-high 23rd double. ... Twins RHP Kevin Correia (4-9, 5.08 ERA) faces LHP Jason Verges (7-3, 3.53) in Wednesday afternoon's series finale.