EAST RUTHERFORD, N.J. -- Another day, another quarterback loss for the New York Jets.

Starting for Sam Darnold, who was diagnosed last week with mononucleosis, Trevor Siemian suffered a potentially serious injury to his left ankle in the Jets' 23-3 loss to the Cleveland Browns on Monday at MetLife Stadium.

Siemian, spotted in the locker room with crutches and a walking boot, will have an MRI exam on Tuesday to determine the extent of the damage. He was injured in the second quarter when his left leg bent awkwardly on a late hit by Browns defensive end Myles Garrett.

Jets coach Adam Gase declined to comment on the severity of the injury.

Siemian was replaced by third-stringer Luke Falk, who was signed off the Jets' practice squad earlier in the day. Falk, who spent the preseason with the Jets, finished 20-of-25 passing for 199 yards in his NFL debut.

"It's familiar territory for me," said Gase, who has started six quarterbacks since 2016 -- four with the Miami Dolphins and two with the Jets.

It probably will be seven, as Falk seems likely to start Sunday against the New England Patriots (2-0).

"I don't feel like thinking about it right this minute," Gase said of the New England matchup.

Only five teams in the Super Bowl era (excluding the 1987 strike season) have had to use three quarterbacks in their first three games. The most recent two teams to do it combined for a 3-29 record; the previous three all made the playoffs.

Chances are the Jets will have to sign a backup quarterback for the game because Darnold will be sidelined. The Jets haven't said when they expect him to return. The second-year quarterback reportedly is hoping that he can play Week 5 against the Philadelphia Eagles; the Jets have their bye in Week 4.

If Falk had been injured in the game, the Jets would've turned to running back Le'Veon Bell as their emergency quarterback.

Siemian's injury looked nasty, but he managed to get up and walk off the field. He limped to the locker room and was officially ruled out in the third quarter.

The Jets (0-2) tried to rally around Siemian after the Darnold bombshell, but the offense sputtered under him, with three straight punts to start the game. He was injured on the fourth series.

Playing for the first time since 2017, Siemian (3-for-6, 3 yards) was rusty from the outset. He was sacked twice and held the ball too long on other plays. On a third-and-15 from the Jets' 32-yard line, he was flushed outside the pocket and heaved a deep pass to tight end Ryan Griffin. Garrett arrived a split-second late -- he was penalized -- and landed on Siemian, who appeared to be in significant pain.

It was a dreadful day for the offense, which crossed midfield only twice in the first three quarters. In two games, Gase's offense has generated 11 points.

"When we look at it, we're going to have to look at all our guys and see who's doing their job and who isn't," Gase said. "If they're not, we have to put some pieces around and change some things up."

Falk (20-for-25, 198 yards) actually did a decent job, considering the circumstances. He got work in practice, behind Siemian, but he had no chance to work with the starters until Monday night. They started him slowly -- five straight running plays -- and gradually opened up the offense.

"Luke is very confident," Gase said. "Once we got out of that first series, you could just tell he was calm. It was like we were at practice."

The Jets leaned on Bell, who had 10 catches for 61 yards and 21 rushes for 68 yards. He also had a fumble deep in Cleveland territory.

Afterward, Bell was visibly frustrated but shifted the blame away from the quarterback upheaval.

"It wasn't the quarterback play. It's just guys being on details," he said. "We had a lot of dropped passes, a lot of false starts, guys not making enough plays, including myself."

If Falk starts Sunday, it will be the 199th pick in the 2018 draft (by the Tennessee Titans) against the 199th pick in the 2000 draft. Falk and Tom Brady are the only two quarterbacks in the past 20 years to be chosen 199th.

Falk called Brady a "source of inspiration," noting that he follows Brady's legendary diet -- but not as strictly as Brady.

"No, I'm 24," he said, "so I eat pizza every now and then."

Wide receiver Demaryius Thomas (hamstring) and linebacker Jordan Jenkins (calf), both of whom left with injuries, also will have MRIs on Tuesday.