Being mired in a five-game losing streak with a short week to get ready for Peyton Manning and the first-place Denver Broncos is tough enough.

The Raiders have to do it without their coach.

Dennis Allen left the team after Sunday’s 20-17 loss to Cleveland to be with his father, who has a serious medical issue. Allen is expected to rejoin the team on Wednesday night and be on the field Thursday when the Raiders (3-9) host the Broncos (9-3).

But until then, offensive coordinator Greg Knapp will oversee the team and defensive coordinator Jason Tarver will map out the defense.

“This is a pretty unique season, both on and off the field, I’ll say that,” Tarver said Monday. “There’s a bunch of adversity and the true character of a man and a coach and whoever is to, no matter what the circumstances, be a pro and handle your business. But I’ve been a part of a lot of different situations, both in this league and in coaching, but there’s some unique things that have happened this year.”

Allen is with his family in the Dallas area helping to care for his 66-year-old father, Grady, a former NFL linebacker with the Atlanta Falcons. Knapp said he texted Allen on Monday morning to pass on good wishes and planned to talk to the coach as the team prepared for the Broncos.