SAN FRANCISCO -- The D-backs completed a three-game sweep of the Giants on Sunday afternoon with a 6-2 win at Oracle Park.

Not all was good for the D-backs, though, as starter Luke Weaver exited in the sixth inning with right forearm tightness, which can often be a precursor of a more serious injury.

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“We’re just gathering information,” D-backs manager Torey Lovullo said. “I can tell you he has forearm tightness, and I really can’t give you any more than that. Very unfortunate, he’s throwing the ball extremely well. We talk to our athletes about being open and honest and transparent and sharing useful information, and he did. He just felt like he was a little uncomfortable and at that point in time.”

An MRI is typically the next step in a situation like this, but after the game, Lovullo said he had not yet had a chance to sit down with the medical staff and the front office to discuss that.

Weaver (4-3) has been one of Arizona’s best starters this season. The 25-year-old was acquired along with Carson Kelly from the Cardinals as part of the trade that sent Paul Goldschmidt to St. Louis.

Weaver, who had allowed one run through the first five innings, gave up a single to Buster Posey to open the sixth and television replays showed him opening and closing his right hand afterward.

“Just felt a little tightness in the forearm,” Weaver said. “I wanted to just really be smart about it. It was a day where it was cold out, the conditions weren’t perfect and kind of the way the ballgame was shaping up, I just wanted to be smart and not do anything stupid.”

Weaver was asked if the final pitch he threw was the only one that caused discomfort.

“A little bit through the game throwing some changeups and sometimes, I think, more than anything, mechanics weren't really feeling great,” Weaver said. “So, sometimes you just put your arm in a spot that’s a little funky. I’m not too concerned. Just feel confident and just making sure that I’m doing the right things, talking to the guys who do this for a living and like I said, just wanted to play it smart. There’s just no need for any heroic acts out there, especially on a day like today.”

The D-backs' rotation depth has already been tested this year.

Right-hander Taijuan Walker, who was expected back next month from Tommy John surgery, recently sustained a sprained shoulder capsule, sidelining him until, at best, late in the season. Then, the struggles of Zack Godley caused the team to send him to the bullpen and bring up Taylor Clarke, who picked up his first career win Saturday afternoon.

If Weaver misses any time, it’s possible the D-backs could put Godley back in the rotation, or they could reach back down to Triple-A Reno for top pitching prospect Jon Duplantier, who has pitched well in three stints in the big leagues this season.

By the time Weaver departed, the D-backs led, 6-1, thanks to an offense that feasted on Giants pitching over the weekend. Arizona scored 34 runs in the series, which set a franchise record for most runs in a three-game road series.

Ketel Marte led the D-backs' offense with a pair of hits, including a homer, his third of the series.

“He’s just on every ball,” Lovullo said. “Ketel’s a special player, and we’re getting an opportunity to watch somebody grow right before our very eyes and turn into a very good player.”