The Los Angeles Chargers were without head coach Jim Harbaugh early Sunday afternoon against the Denver Broncos.

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. No further details about his illness are known. 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 will be playing his first season with the Chargers this fall after spending nine years at Michigan and winning the national championship last year. It’s his first job back in the league after managing the San Francisco 49ers for four seasons from 2011 to 2014. The Chargers entered Sunday’s game with a 2-2 record.