SAN FRANCISCO -- Jurickson Profar's ability to play first base, a responsibility that he's likely to handle part-time for the A's, shouldn't come as a surprise.

That's the unshakable opinion of Giants bench coach Hensley Meulens, who managed Profar in 2013 and 2017 when they represented the Netherlands in the World Baseball Classic.

Profar, known primarily as a middle infielder, started at first base in Monday's Bay Bridge Series exhibition against the Giants at Oracle Park. He committed a harmless third-inning error on Joe Panik's grounder during Oakland's 5-4 victory. It was Profar's initial activity at first base since Matt Olson sustained a broken right hand last Thursday. Olson is expected to be sidelined for four to eight weeks.

A's manager Bob Melvin plans to use Mark Canha and Profar as the primary first-base substitutes while Olson heals. Profar, who joined the A's from Texas in a three-team trade last Dec. 21, has appeared in 43 career games at first base, starting 33.

"He's so athletic that he moves around the entire field," Meulens said. "He has made some great splits over there, playing first. You have to watch some of his film playing first."

Asked if he really executed the splits to help himself reach for a throw or a ground ball, Profar laughed.

"Sometimes," he said.

Profar has played five positions -- all four infield spots besides left field -- in each of the previous three seasons.

"He's able to do that because he's athletic and he loves playing," Meulens said. "He knows where to position himself. He reads bats. He's a quick learner besides being a very smart player."

• Predictably, Melvin officially awarded the fourth starter's role to Frankie Montas.

"Deservedly so," Melvin said of Montas, who recorded a 0.56 ERA and 16 strikeouts in 16 innings spanning five exhibition appearances. The 26-year-old right-hander sealed his status by pitching three no-hit innings Sunday against the Giants.

Explaining his decision, Melvin said, "He throws 97 [mph], start with that. But I think what's made him who he is now is adding the split-finger [fastball] and being a three-pitch guy with the slider and having command of all three of them."

As for assigning the fifth starter's role, Melvin said the A's are "not there yet."

• Melvin added that the A's have not discussed the prospect of using an "opener" -- a reliever who would pitch a low number of innings to begin a game -- despite beginning the U.S. portion of the regular season with 18 consecutive games. But he didn't rule out that possibility.