PITTSBURGH -- The A’s have two of the most electric arms to try to close out wins in Lou Trivino and Blake Treinen. But the question this year has been who to use before the dynamic duo.

After the A’s struck for three runs in the first inning, the Pirates slowly rallied back with three runs off starter Chris Bassitt, then three runs off J.B. Wendelken, handing Oakland a 6-4 loss at PNC Park.

It didn’t help that Treinen was unavailable Saturday night and likely will be Sunday, too, as A’s manager Bob Melvin said the closer is dealing with right elbow soreness. He’ll be evaluated on Monday in Oakland, but that meant Trivino was the de facto closer in a save situation on Saturday.

So there were two possibilities from a pitching standpoint to best put the A’s in a position to hand the ball to Trivino: Have their starter, Bassitt, go deep and limit the Pirates’ run production, or have the bullpen show up clutch for a few innings.

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Neither of those things came to fruition, as Bassitt and Wendelken -- two players who have broken out over the past two years with the A’s -- gave up crucial hits.

Bassitt for the most part worked his way around runners reaching base, but Josh Bell had the right-hander’s number, teeing off for two homers to score every Pirates run off the starter.

Both pitches Bell squared up were center-cut fastballs -- a cutter and sinker -- that he drove a projected 379 feet and 451 feet, per Statcast, respectively. Those hanging fastballs were a symptom of a larger command problem for Bassitt.

“I missed spots against everyone tonight,” he said. “I got really lucky a couple of times, but Bell made me pay.

“Mechanically, I felt right. Physically, I felt really strong. It was just I felt a little off. As weird as it was, I felt too loose.”

Liam Hendriks came on in relief of Bassitt and blanked the Pirates in the sixth, though he had to do it with one out and the bases loaded after two hits and an intentional walk.

But Wendelken didn’t match Hendriks’ success with men on base. He allowed a one-out double to Gregory Polanco, then got the second out on a fielder’s choice to put runners on the corners. Kevin Newman, who entered after pinch-running the inning before, delivered a crucial two-run triple the next at-bat that gave the Pirates the game-winning run.

“I was just trying to stay low and away, get a ground ball in that situation, and it’s just unfortunate that he got up under it and pushed it down the line,” Wendelken said. “Not much I could do about it. Just a good pitch and a good piece of hitting.”

The A’s righty had drawn comparisons to Trivino, as he came out of the blue and pitched lights out in 2018. He allowed only one run over 16 2/3 innings, but this year he’s given up 14 runs (13 earned) in 20 innings, including six runs in his past two outings.

For his part, Wendelken is not alarmed about the struggles yet.

“I just need to stay on top, get drive down, get through the ball a little bit more,” he said. “Maybe it puts a little more deception back into my ball, because right now it’s gotten away from me.

“Small fixes, but easy fixes. It can be done in a single day if I really get out there and get after it.”

Even after Francisco Cervelli knocked in Newman with a single, Melvin stuck with Wendelken to get the final out.

“He’s going through a rough patch. Still, we’ve got a lot of faith in him getting that last out right there,” Melvin said.

With the way Bassitt and Wendelken have shown dominance in recent history, four runs would typically be enough to power a win. And that’s what was so hard to stomach for Bassitt.

“Overall, just a really frustrating night, because the way our offense played, I kind of gave away a win, to be quite honest with you,” he said. “Can’t really happen. It has to be a win.”

Worth noting

• In his father’s childhood hometown, Skye Bolt knocked a double high off the Clemente Wall for his first Major League hit. He appeared to slow up as he rounded first base, and he admitted he thought it had gotten out. “Bottom line is I’ve got to start doing homework on my ballparks,” he said. “I’ve gotten a fair amount of grief about it, and hey, for a first hit, I guess it’s got a story behind it.”

• Kendrys Morales continued his turnaround this season with two hits on Saturday, including an RBI triple in the first, his first triple since Sept. 20, 2015. He’s now 5-for-8 in his past two games after going 3-for-41 in his previous 14 games.