Nothing like a shutout to get back on track.
"I'm just trying to be consistent," Diamond said. "My approach right now is to be as simple as I can be, and because of that I've been consistent."
The former Rule 5 draft pick looked just as strong after his chance for a perfect game ended.
"At that point, it was just trying to get us a win," Diamond said. "I just tried to keep going, go as deep as I could."
Hafner had two hits for the Indians, who lost for the second time in six games.
Diamond allowed just one baserunner after the fifth, striking out six and notching his first career shutout.
After going 5-1 with a 1.61 ERA in his first seven starts, Diamond had a 4.86 ERA in his last seven, including two bad outings after the All-Star break.
He was back to his pre-All Star Game form on Friday, needing just 98 pitches to go the distance.
"We couldn't do anything against him," Cleveland manager Manny Acta said.
Cleveland has been shut out five times this season, all since June 9.
Morneau gave the Twins a 3-0 lead in the first with his first home run since July 6, a 421-foot drive that was caught by a fan on the Target Field plaza in right field.
The Twins followed with five runs in the fourth off starter Josh Tomlin (5-8), capped by Willingham's 26th home run.
Tomlin allowed a career-worst eight runs in four innings and lost for the fifth time in his last seven decisions.
"You don't want to go out there and have a season like this," said Tomlin, who has an 11.65 ERA in the first inning and a 5.87 ERA overall. "You can say this stuff happens every now and then or people have bad years, but today was inexcusable to me. That was just a bad performance."
Acta didn't say that Tomlin won't be making his next start, but did say that he will sit down and "look at all the options."
Reliever Jeremy Accardo didn't fare much better as the Twins added three more in the sixth and finished with 15 hits.
The Indians entered Friday 3½ games behind in the AL Central after Carlos Santana and Hafner hit home runs on consecutive pitches to ignite a late rally against Justin Verlander and Detroit Tigers on Thursday.
"One more example that every day is a new day in baseball. Theres no such thing as momentum," Acta said.
Friday's loss snapped a five-game winning streak at Target Field and was Cleveland's worst since losing 12-1 at Boston on May 13.
The AL-worst Twins are just 5-11 since July 7 and have fewer wins than they did at this point in last year's 99-loss season.
With Diamond one of the few bright spots in the rotation, the Twins will need more home runs from Morneau and Willingham if they want to avoid surpassing last season's loss total.
"It starts with those big guys," manager Ron Gardenhire said. "When they put it in the seats, it makes things much easier."
Twins third baseman Trevor Plouffe was a late scratch after aggravating a right thumb injury that has kept him out since July 20. He was placed on the 15-day disabled list, retroactive to July 21.
The Twins recalled OF Danny Valencia from Triple-A Rochester to replace Plouffe. ... An MRI on Indians LHP Rafael Perez's strained left lat showed no further damage. Out since April 26, Perez reported shoulder fatigue during his rehab and will be shut down for three to five days. ... According to the Elias Sports Bureau, Hafner and Santana are the first two players to ever homer on consecutive pitches against Verlander. ... Minnesota's Samuel Deduno (1-0, 3.94 ERA) faces Justin Masterson (7-8, 4.12) on Saturday night. Deduno earned his first career win in his last start. Masterson is 7-6 with a 3.63 ERA over his last 17 starts.