LONDON -- Washington Commanders quarterback Marcus Mariota injured the medial collateral ligament in his right knee, the same one that caused him to miss multiple weeks in training camp, in Sunday's 30-13 loss to the Indianapolis Colts.
Commanders coach Dan Quinn said Mariota would undergo more tests Monday.
Quinn also said Jayden Daniels, who missed his second consecutive game with a dislocated left elbow, could return against the Giants in Week 5 after what they say will be a full week of practice. He was limited in practice this past week.
"That's the hope for sure," Quinn said of Daniels playing next week, adding that a decision on whether or not to sign another veteran backup would be based on what Mariota's tests show.
Mariota's right knee appeared to bend as he was sacked by defensive tackle Adetomiwa Adebawore on third-and-goal from the 6-yard line. Mariota did walk on his own into the locker room after being examined in the medical tent.
"It's a significant change [offensively] because you don't do quite the same [things]," Quinn said after the Commanders fell to 1-3. "He was off to an excellent start, but it's a factor for sure."
Mariota sprained the MCL in the same knee during the first preseason game on Aug. 15. He did not play the rest of the preseason and returned to practice on Aug. 31.
Sunday, Mariota was able to walk to the locker room, but he was ruled out at halftime. In two series, he threw for 46 yards and had a 35-yard run on a zone-read keeper to set up a field goal.
He was replaced by rookie seventh-round pick Athan Kaliakmanis, playing for the first time. He completed 15 of 33 passes for 186 yards, one touchdown and an interception.
But, Quinn said, it changes what they can run offensively. Mariota has more ability to run than Kaliakmanis -- evident by the 35-yard run early on his second and final series. But Mariota also was praised last week in a 33-31 win over Seattle for how he handled all aspects -- from protections to adjusting post-snap and more.
It's harder to expect that from Kaliakmanis in his first start. He said he knows the Colts tested the Rutgers product with more pressure packages. It tested the line as well.
"Teams see a quarterback come in, they try to heat them up," left tackle Brandon Coleman said.
Kaliakmanis attempted six passes of 35 or more air yards -- the most in a game since Russell Wilson did it in 2021. Kaliakmanis completed two of those for 95 yards, including a 47-yarder for a touchdown to Trey Burks.
"Losing your QB is always tough," Coleman said. "It sucks ... [But Kaliakmanis] was balling out. He got comfortable. It's up to us to make sure he stays comfortable."
Kaliakmanis' day was more complicated because Washington was playing minus receiver Terry McLaurin, who injured his hamstring Friday, and right guard Sam Cosmi, who missed a second consecutive game with a concussion. Rookie Matt Gulbin started at right guard. But Kaliakmanis said he felt ready.
"When a chance like this comes [and you prepare], then you're ready," he said. "I didn't play my best game today by any stretch. There's a lot of work to do and that's for sure. And I can't wait to get back after it."
Defensive end Charles Omenihu (groin) was also ruled out during halftime, and wide receiver Jaylin Lane was carted off in the third quarter after suffering what Quinn later termed a "serious" ankle injury.
The Commanders are in a difficult spot with upcoming games against San Francisco, Philadelphia and the Rams. After what Quinn termed a strong week of practice -- and with momentum after upsetting Seattle -- Sunday was a letdown because of the loss and more injuries.
Quinn looked disheartened after the game, but continued to express confidence.
"A good fire has been lit and so it will stay lit," he said. "It has not dampened my belief in them in any way. But it is difficult to overcome some of the injuries, but I'm certain these are the right guys that battle and fight for it. They are one of the more connected groups I've been around and that will be really important to move us forward."