– Mike Pelfrey’s anniversary party was rolling along nicely on Monday, full of auspicious episodes and poignant moments.

And then Prince Fielder crashed the joint.

Pelfrey marked the one-year milestone since a surgeon replaced his elbow ligament with a new one by throwing five strong innings against the defending American League champions. But Fielder spoiled the occasion by blasting Pelfrey’s worst mistake — a 90-miles-per-hour sinker that didn’t — 400 feet to left-center for a three-run homer that delivered Detroit to a 4-3 victory over the Twins at Comerica Park.

The actual anniversary of Pelfrey’s Tommy John surgery comes Wednesday, and maybe by then he can enjoy looking back on everything that went right, like all the sinkers that helped him induce nine ground-ball outs, or the nine- and seven-pitch innings he cruised through, or the two occasions he left Tigers stranded in scoring position. But he probably is going to be dwelling on that pitch to Fielder.

“A terrible pitch there. And he made me pay for it,” said the Twins righthander, now 2-3 in his comeback season. “It was the worst possible pitch you could make there. I was trying to get a ground ball, but I threw it right down the middle and it stayed up.”

The pitch ruined what had been Pelfrey’s most encouraging start — “Tonight was a step forward, definitely,” said manager Ron Gardenhire — in a month of frustrating performances. Pelfrey came in with a 7.94 ERA and had yet to pitch six complete innings. “It’s been a bad month,” he said. “I’ve had worse, but it’s unacceptable.”

It appeared things had changed, however. He threw a slider that got too much of the plate, which Andy Dirks lined into the right-field stands, but other than that, had limited a batting order that leads the AL in hitting to a couple of singles and a two-out triple.

But with the Twins up 3-1, Dirks led off the bottom of the sixth by bunting the ball up the third-base line for a hit. Pelfrey then got Cabrera to hit a towering pop-up in foul ground behind first base, but with first baseman Justin Morneau and right fielder Chris Parmelee playing the reigning MVP to pull, neither could reach it, giving Cabrera new life. Pelfrey ended up walking him, and pitching coach Rick Anderson visited the mound.

“He said, ‘Let’s get a ground ball,’ ” Pelfrey said. “The best way for me to do that is with a sinker. And I just didn’t execute.”

Still, the outing was a hopeful one. Pelfrey worked noticeably quicker, and had better movement on his breaking pitches. “He was on top of the ball, it was sinking, and he stayed strong throughout,” Gardenhire said. “But that’s what that lineup over there can do — one pitch.”

The Twins got a solo home run from Josh Willingham in the first inning, but that was all the top of the order could do against Tigers righthander Max Scherzer. He struck out 10, walked nobody and held the first four hitters in the Twins lineup to 1-for-16.

Most notable among those outs: The four made by Joe Mauer, giving him 20 consecutive at-bats without a hit. That’s the longest hitless streak of his career, beating out a streak of 17 at-bats in 2007, and was the capper to a night in which he also caught two foul balls right on the mask, briefly shaking him up.

Mauer’s average midway through last Tuesday night’s loss to Miami stood at .371, but like the snow that fell that day, it’s been melting ever since. It stands at .289 going into Tuesday’s game — against Justin Verlander.