The Los Angeles Chargers were without head coach Jim Harbaugh early on Sunday afternoon in their 23-16 win over the Denver Broncos.

Harbaugh, minutes before their game started at Empower Field at Mile High in Colorado, was seen entering the team’s blue medical tent on the sidelines to get checked out. It was unclear what the issue was at the time, and Harbaugh walked back to the locker room minutes later. He missed the start of the game as a result.

A few minutes into the game, the Chargers then confirmed that Harbaugh was dealing with an illness and was questionable to return. Defensive coordinator Jesse Minter stepped in to serve as the team’s interim head coach in the meantime.

Harbaugh’s brother, Baltimore Ravens head coach John Harbaugh, ended his news conference abruptly after learning of the situation in Denver, too. John was speaking after the Ravens’ 30-23 win over the Washington Commanders, and he left to call his brother and check in, according to The Athletic’s Jeff Zrebiec. It’s unclear if he got through or was able to speak to Jim.

Just past the midway point of the first quarter, Harbaugh returned to the sidelines and took back over. He came back out just in time to watch quarterback Justin Herbert throw a 38-yard touchdown pass to Kimani Vidal, too, which put the Chargers up 10-0.

Harbaugh told CBS that he was dealing with an arrhythmia, which is an irregular heartbeat. Harbaugh said he has been dealing with one on and off for “a while.” He said after the game that he experienced an atrial flutter, which is when the abnormality causes the upper chambers of the heart beat too quickly.

“I got into an episode today with it,” Harbaugh said. “Doctors checked me out, and it got back into sinus rhythm, normal rhythm, so I came back.”

Harbaugh said he will have a follow-up appointment with doctors on Monday to determine his status and the severity of his arrhythmia on Monday.

Harbaugh is in his first season with the Chargers this fall after a nine-year run at Michigan, which he capped with a national championship in January. It marks his first job back in the league after he spent four seasons leading the San Francisco 49ers from 2011-2014. Harbaugh said he experienced a similar arrhythmia during a “Monday Night Football” game with the 49ers. The 49ers beat the Chicago Bears that night, which is a game Harbaugh said he will always remember.

“I’m 2-0 with arrhythmias,” Harbaugh said with a laugh.

After their quick start, the Chargers held on late to grab the seven-point win on Sunday afternoon in Denver. They put up 23 unanswered points to start the game, thanks to a pair of field goals from Cameron Dicker and a 4-yard touchdown run from J.K. Dobbins after Vidal’s touchdown, before the Broncos finally put points on the board. Justin Herbert went 21-of-34 for 237 yards with a touchdown pass. Dobbins finished with 96 yards and a score on 25 carries, too. The win snapped a two-game losing skid for the Chargers and pushed them to 3-2 on the season.

Bo Nix went 19-of-33 for 216 with two touchdowns and an interception in the loss for the Broncos. Both of his touchdown passes came in the fourth quarter. Courtland Sutton, who finished with 53 yards on four catches, caught one of them on a wild one-handed grab in the back of the end zone.

The Broncos, who had won three straight entering Sunday, are now 3-3 on the season.