Opening Day got a little testy in Oakland.

Video has emerged of Angels star Anthony Rendon in an altercation with an Athletic fan after Los Angeles’ season-opening loss at O.co Coliseum, with the infielder grabbing the fan’s shirt as he walked off the field.

“You called me a bitch, huh?” Rendon said to the individual, who denied the third baseman’s charge. “Yeah, you did. Yeah, you did. Yeah, mother f–ker.”

Warning: Video contains explicit language.

Rendon let go — but quickly took a swipe at the fan, telling him to “get your bitch-ass out of here.”

According to The Athletic, Major League Baseball is looking into the altercation.

The Angels told TMZ Friday that they had no comment regarding the 12-second clip, which is currently circulating on social media.

Oakland Police told the outlet they are looking into the incident.

“Although we are still unaware who the victim is,” an OPD spokesperson said in a statement on Friday afternoon, “surveillance video of the incident has surfaced. As a result, OPD created an incident, made a report, and is actively investigating.”

Rendon, 32, is entering his fourth season with the Angels after signing a seven-year, $25 million deal to lure him away from the Nationals in 2020.

Injuries have limited him to just 158 games over that span — he has yet to play more than 58 games in a single season for Los Angeles.

A two-time Silver Slugger award winner and 2019 World Series champion with Washington, Rendon has struggled when in the Angles’ lineup.

His .250 batting average is 40 points off of his Nationals’ tenure, while his slugging percentage of .417 is a stark drop-off from his .490 in D.C.

Rendon finished Thursday’s 2-1 loss by going 0 for 3 with a walk from the cleanup spot behind Shohei Ohtani.

Ohtani, the Angels superstar, also threw for six innings of a two-hit ball game, striking out 10 without giving up a run in the Opening Day effort —adding a 1 for 3 mark with an intentional walk at the plate.

Much like Rendon, Ohtani and the rest of the Angels were seemingly unhappy with the result.

“We got a lot of guys on base and had guys in scoring position but lacked that one big hit,” said Ohtani. “Obviously, we wanted to score more.”

The Angels are off Friday, but will play the second of a three-game set against the A’s on Saturday at 4:07 p.m. ET.