SAN FRANCISCO – Sunday marked one month since the Twins most recently ascended to first place in the AL Central, a position they haven't surrendered since. It also wrapped up yet another successful road trip, a 6-4 West Coast getaway that frequently demonstrated how and why they got to such an unexpected lofty position.

But ultimately, the finale also illustrated one weird idiosyncrasy of this team, one that raises doubts about their security at the top: When they lose, boy, they do it with gusto.

"It's been a very volatile year, that's for sure," said veteran Matt Belisle, whose own season mirrors his team's bizarre tendency to crash and burn. "I've never had a year like this."

Charged with shepherding a one-run lead in the seventh inning, Belisle drove it off a cliff instead, surrendering four runs that doomed the Twins to another rout, 13-8 to the Giants. And so the Twins leave you wondering: If they are so good, why are they often so bad?

"We seem to give up some really big numbers," said Paul Molitor, whose team is 30-25 yet has been outscored by 28 runs, the third-worst differential in the AL. "I don't think we've played as well as we're capable of, but we're getting better."

This trip was a perfect example: The Twins could have gone 8-2. Twice the bullpen failed to protect a late-inning lead, once on a walk-off homer at Seattle, a one-pitch blunder by closer Brandon Kintzler. Sunday's game was another one of those bullpen meltdowns the Twins have experienced with startling regularity this season.

Nine times in 2017, they have given up 11 or more runs — already equaling their total from their disastrous 2016. And individual Twins relievers have given up three or more runs in an outing an MLB-high 18 times.

This time the culprits were Belisle, who absorbed a four-run, four-hit beating in the seventh inning, and Craig Breslow, who doused any chance of a comeback by surrendering five runs in the eighth. The Twins got home runs from Eduardo Escobar and Byron Buxton, a go-ahead two-run single by Robbie Grossman and a so-so start by Nik Turley. But the bullpen undid it all.

Belisle is bewildering, Molitor said; he has more scoreless relief innings than any Twin but Kintzler. He pitched five times on the trip and put up a zero in four of them. But Sunday? Splat.

"You saw his last few outings, they've been good," Molitor said. "He's been at the far ends of the spectrum — either lights-out or things get compounded."

Yes, compounded. That's what Buster Posey did to Belisle in the seventh, after a leadoff walk to Kelby Tomlinson — "No excuse there, that's on me," Belisle said — and an infield single by Eduardo Nunez. Aaron Hill popped out, but Posey shot a double to left, putting the Giants ahead for good.

"I did exactly what I wanted to do. I wanted to get a ground ball to that side, I wanted him to hit the ball to [Miguel] Sano," Belisle said. "So that's baseball — I threw the pitch I wanted, and we got the ground ball."

Hunter Pence followed with an RBI double, and Austin Slater singled him home, boosting Belisle's ERA to 8.59 due to eruptions of five, six, three and four runs. That's four ugly outings — he's never had more than five in any other season.

"I'm really, really good at saddling back up and putting yesterday behind me," Belisle said. "If anything, the volatility is going to make me stronger about how to be resilient and keep going."