"I don't really care how we win a game, to be honest with you, but today was a good example of us not folding tents," Willingham said. "Joe had the at-bat that set the inning up by getting on base and gave me a chance. We showed some resiliency."
Chapman has now blown three of his last five save opportunities and has an 11.80 ERA in his last seven appearances. But he seemed to have put those troubles behind him to start off the ninth.
Mauer fell behind, 0-2, after Darin Mastroianni had struck out to begin the inning. But Mauer battled back, fouling off four fastballs, three of which were clocked at 100 mph or higher on the stadium radar gun, and laying off three sliders out of the strike zone to run the count full.
"I wanted to stay short," said Mauer, echoing Willingham's approach against Chapman. "He kept coming right after me. He's got a great arm and it's hard to think you can go into a slump with that kind of stuff."
Mauer hit pitch No. 10 off the left-field wall for his 232nd career double, tying him with Harmon Killebrew for ninth-most in Twins history.
"The game was the at-bat that Mauer had," Reds manager Dusty Baker said. "That was a tremendous battle right there that we didn't win."
Diamond improved to 6-3 and ended a personal two-game losing streak. The victory also allowed the Twins to end their six-game road trip at .500, 3-3.
Jared Burton walked two, but earned his first Major League save with a scoreless ninth inning.
Justin Morneau's RBI groundout in the seventh inning had given the Twins the lead for the first time in the game. Mauer singled to right field to lead off the inning and went to third on a double by Willingham prior to Morneau's groundout.
Trevor Plouffe hit his 15th home run of the season and 10th of June with one out in the fifth inning off Cincinnati starter Mike Leake to even the score 1. Plouffe had struck out his previous four at-bats, including three times on Saturday.
Diamond had been roughed up in his last two starts, allowing eight earned runs on 13 hits in 11 1/3 innings, but continued his streak of dominant pitching in the daylight. He was 3-0 with a 1.03 ERA in four previous daytime starts this season and did nothing to damage those numbers on Sunday until Votto's home run. He allowed three runs on eight hits while striking out a career-high seven in his eight innings.
"From my pitch to Votto to Willingham going off and then Burton closing it down was pretty exciting," Diamond said. "Pace was something me and [pitching coach Rick Anderson] focused on during this week's bullpen. We were trying to keep the pace going and keep things simple. That was the mentality, to get back on the mound and keep going. We were able to keep the game rolling."
Diamond allowed a single run in the third inning. Reds catcher Devin Mesoraco led off with a double. Leake put down a sacrifice bunt to send Mesoraco to third base, where he scored on Wilson Valdez's single to right field with two outs. Diamond hit Votto (on an 0-2 pitch) and Brandon Phillips in consecutive at-bats to load the bases, but got out of the inning when Jay Bruce flew out to Willingham in left field.
Diamond bounced back with a 1-2-3 fourth inning and got some defensive help in the sixth inning to keep the Reds at bay.
Bruce singled with one out in the sixth, but was thrown out at the plate attempting to score on a double by Ryan Ludwick. Cincinnati third-base coach Mark Berry sent Bruce home even though Willingham cleanly fielded the ball in the left-field corner. Willingham made a perfect relay to shortstop Brian Dozier, who threw on to Mauer waiting at the plate to apply the tag on Bruce.
"I was just trying to get to the ball as quick as possible and get the ball as quick as possible to our shortstop," said Willingham. "When I saw the ball in the air and I saw them waving him, I thought if we had a good throw, we're going to get him out."