DETROIT -- Logan Webb was cruising along during Wednesday’s finale at Comerica Park, his difficult last start a thing of the past as he carved through the Tigers’ lineup again and again.

The Giants’ No. 2 starter took a no-hitter into the fifth inning, fanned six Tigers and seemed fully capable of rounding out the 1-2 punch that rotation frontman Carlos Rodón had begun one night prior as San Francisco moved in to cap a two-game sweep.

Which made the speed at which everything unraveled during the 6-1 defeat that much more surprising.

“It kind of just happens,” Webb said. “I can’t really explain it; it just wasn’t very good.”

Webb lost the no-hit bid on a one-out single in the fifth inning, but it couldn’t be helped: Jeimer Candelario tapped a ball through a sparsely occupied left side, beating the shift. When Tucker Barnhart followed with a double to right to put runners at the corners, though, Webb was visibly frustrated, angrily windmilling the ball toward the visitors' dugout and calling for another.

After walking the bases loaded, Webb caught leadoff batter Riley Greene looking at a third-strike slider that nipped the outside of the zone to give hope that he’d emerge from the rocky frame with no real damage.

But three consecutive singles dashed those thoughts, plated four runs and left manager Gabe Kapler hesitating at the top of the dugout steps, because while it was clear Webb was done, it also didn’t seem like Thomas Szapucki had gotten enough time to warm in the bullpen.

Szapucki threw just five pitches before a Willi Castro double pushed Detroit’s lead to 6-0.

All runs were charged to Webb.

All came with two outs.

But not everything was Webb’s fault.

“Some falling behind [in the count], some [balls] falling in some holes,” manager Gabe Kapler said. “I think when Logan’s ahead in the count, he’s getting more swings and misses, so there’s some contact in that inning. Some of it was unfortunate; some of it was hard.”

This is not what the Giants needed, both in terms of a rebound outing from Webb and a step forward in a National League Wild Card race that has them on the outside looking in. With four teams in front of San Francisco and two standing between the club and a postseason berth, games against teams like the Tigers -- who sit 29 games below .500 -- are must-wins.

Heck, with 39 regular-season games to go, most of the Giants’ games are must-wins.

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Webb’s afternoon started innocently enough. The 25-year-old sat down the first seven Tigers he saw in order using a balanced combination of sinkers, sliders and changeups. Kapler said before the game that Webb is at his best when he’s filling the strike zone, and his starter did just that.

With Webb’s tendency to both pitch to contact and induce grounders, the onus was on the defense to hold up its end of the bargain. The Giants played errorless defense on paper, but Victor Reyes’ two-run chopper up the middle -- the one that started the scoring avalanche -- had just a 45 percent hit probability when it bounded up and over shortstop Brandon Crawford.

“That’s just part of baseball,” Webb said. “With the way I throw, that stuff’s going to happen every now and then. Usually, when it happens, I try to limit it, and I just didn’t do a very good job of that.”

There were also a couple of hit-‘em-where-they-ain’t plays in the fifth, including Harold Castro’s run-scoring knock that scooted barely beyond a diving Crawford, and Barnhart’s double that bounced just past sprinting second baseman Thairo Estrada’s fully extended glove and into right field.

One bad inning. A couple of bad hops. Still, a loss is a loss no matter how it shakes out, and San Francisco can’t afford to weather many more winnable defeats if it plans on playing mid-October baseball.

“You have to look at [the playoff race] as a great opportunity,” Kapler said, “and that's still where we are. I'm not going to say we're in the position we wanted to be when the season began because we'd like to be out in front, somehow, some way.

“But that's not where we are, and that means we have to play really good baseball down the stretch.”