Mariota (knee) has been ruled out for the remainder of Sunday's game against the Colts in London, Tashan Reed of The Washington Post reports.
Mariota left the game midway through the first quarter, after he appeared to injure his right knee on a sack. With Jayden Daniels (elbow) inactive for a second straight game and with Mariota -- who previously dealt with an MCL sprain in the same knee during the preseason -- set to miss the final two quarters of Sunday's contest, rookie seventh-round pick Athan Kaliakmanis will be the lone healthy quarterback available for Washington. Mariota will finish Week 4 with three completions on four attempts for 46 yards and one carry for 35 yards.