OAKLAND -- Some losses carry a bit more weight than others. For the A’s, who find themselves in a tight playoff race with just over a month left in the regular season, Saturday’s was about as frustrating as it gets.

The A’s have developed a formula that has led to victory so often this year: build an early lead and hand it off to a deep bullpen to close it out. It worked in Friday’s Bay Bridge Series opener against the Giants. But on Saturday, those plans went awry.

A three-run lead carried by the A’s into the seventh inning slowly began to dwindle, as back-to-back homers surrendered by Andrew Chafin cut the lead to one. Though Jake Diekman maneuvered his way out of a tough jam in the eighth, Lou Trivino was unable to make a one-run lead stick as he allowed a two-run, pinch-hit homer to LaMonte Wade Jr., resulting in his first blown save since May 31 and putting the Giants ahead for good in a 6-5 loss at the Coliseum.

On a day that saw both the Astros and Yankees come away victorious in their games, the A’s stunning defeat dropped them to 3 1/2 games back of Houston for first place in the American League West and a full two games back of New York, which leads the AL Wild Card race. The Red Sox also lost their game, so the A's maintained a half-game lead on Boston for the second Wild Card spot.

“We needed to win that game,” Trivino said. “It sucks, quite frankly. We had the lead most of the game and felt we were on a roll. It hurts a little more.”

Trivino, who was pitching a third day in a row for the first time this season, displayed a slight decrease in velocity from his season average. Entering the bottom of the ninth holding a one-run lead, he issued a one-out walk to Brandon Belt before giving up the go-ahead two-run blast to Wade Jr. in a 1-1 count on a 94 mph cutter thrown up and on the inner part of the zone.

“I wanted to throw it up in the zone,” Trivino said. “You don’t want to throw a lefty down and in, because they tend to hit that well. But apparently, they also hit 94 [mph] up and in pretty well, too. It is what it is.”

A late lead surrendered by any members of the A’s bullpen is a rarity these days. The fact that it was Trivino and Chafin who faltered made it even more surprising.

Prior to Saturday’s blown save, Trivino had converted each of his last 14 save opportunities dating back to June 5, posting a 0.84 ERA (three earned runs in 32 innings) over that stretch. Meanwhile, Chafin, who has impressed since he was acquired last month in a trade with the Cubs, had allowed just one home run in 49 2/3 innings pitched this season and no earned runs since joining the A’s.

Of Chafin’s two homers allowed on Saturday, the first came from Belt, who entered the day hitless against the left-hander in 16 career at-bats. Darin Ruf hit the other solo homer.

“Maybe a few balls up,” A’s manager Bob Melvin said of Chafin’s stuff. “Belt is a good low-ball hitter. It was a good matchup. But he got a ball that he can handle, and then maybe the ball to Ruf was up a little bit."

The Giants, who entered the day leading the Majors in home runs, scored all six of their runs via the long ball.

“You have to be pretty fine against them,” Melvin said. “That’s a good home run-hitting team. When they got some mistakes, they took advantage of them.”

This bump in the road for the A’s bullpen could be an underlying effect of a recent inability of the starting staff to pitch deep into games. Over the last nine games, the A’s have had just one starting pitcher complete six innings.

On Saturday, Sean Manaea was provided an early lead with a three-run first inning by the A’s offense that was once again sparked by Starling Marte, who after doubling home the game’s first run stole third base and later scored on a two-run single by Seth Brown.

Yet after laboring through the early innings, the left-hander was pulled with two outs in the fifth after he loaded the bases on two walks and a hit-by-pitch, with Yusmeiro Petit coming on in relief to escape the jam and preserve a three-run lead at the time.

With the bullpen having to cover so many innings over the past week, Sunday’s series finale against the Giants becomes an important one for Frankie Montas. Perhaps just as important as a series win would mean to the A’s, they could also really use a deep outing from the right-hander to provide the relief corps with a breather.

“We’ve had to run our bullpen out there a little bit,” Melvin said. “[The starters] had been keeping our bullpen rested for the better part of a year. With [Chris Bassitt] out, we’re gonna have to get some guys going deeper in games. It hasn’t happened the first two games here, so we’re looking for a longer outing out of Frankie.”