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

Harbaugh was seen minutes before the game began at Empower Field at Mile High in Colorado, entering the team’s blue medical tent on the sidelines to be examined. It was unclear at the time what it was about, and Harbaugh went back to the locker room minutes later. As a result, he missed the start of the game.

A few minutes into the game, the Chargers confirmed that Harbaugh was suffering from an illness and was questionable about returning. Meanwhile, defensive coordinator Jesse Minter stepped in as the team’s interim head coach.

Harbaugh’s brother, Baltimore Ravens head coach John Harbaugh, abruptly ended his press conference after also learning of the situation in Denver. According to The Athletic’s Jeff Zrebiec, after the Ravens’ 30-23 win, John was talking about the Washington Commanders and went to call his brother to check in. It’s unclear whether he got through or was able to speak to Jim.

Just after halfway through the first quarter, Harbaugh returned to the sideline and took the lead again. He returned just in time to see quarterback Justin Herbert also throw a 38-yard touchdown pass to Kimani Vidal, giving the Chargers a 10-0 lead.

Harbaugh told CBS that he was struggling with arrhythmia, which is an irregular heartbeat. Harbaugh said he has been struggling with such an issue “for quite a while.” He said after the game that he felt atrial flutter, in which the abnormality causes the upper chambers of the heart to beat too quickly.

“I got into an episode with this today,” Harbaugh said. “The doctors examined me and it went back into sinus rhythm, the 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 cardiac arrhythmias.

Harbaugh will play his first season with the Chargers this fall after playing nine years at Michigan and winning the national championship in January. It’s his first job back in the league after managing the San Francisco 49ers for four seasons from 2011 to 2014. Harbaugh said he experienced a similar cardiac arrhythmia during a “Monday Night Football” game with the 49ers. The 49ers defeated the Chicago Bears that night, a game Harbaugh will always remember.

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

After their fast start, the Chargers held on late and took the seven-point win in Denver on Sunday afternoon. Thanks to two field goals from Cameron Dicker and a 4-yard touchdown run from JK Dobbins after Vidal’s touchdown, they scored 23 unanswered points early in the game before the Broncos finally put points on the board. Justin Herbert went 21 of 34 for 237 yards with one touchdown pass. Dobbins finished the game with 96 yards and a score on 25 carries. The win snapped the Chargers’ two-game losing streak and moved them to 3-2 on the season.

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

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