In a shocking development, New York Jets head coach Adam Gase told the media on Thursday that quarterback Sam Darnold would miss Monday night's primetime matchup with the Cleveland Browns due to mono. 

Gase knew that this news was going to surprise people, and appeared upset as he delivered the update. 

"And then [Darnold] ... has mono. He will be out for this game," said Gase. "So Trevor (Siemian) will be starting and Luke Falk will get elevated at some point and be the backup. So, that will be that."

To make matters worse, Darnold has already lost weight, and Gase made it seem like his franchise quarterback is going to miss several games. Per Rich Cimini, Gase mentioned that he's glad the Jets have a Week 4 bye, which could suggest that he's not counting on Darnold until Week 5 when the Jets travel to Philadelphia. 

Darnold completed 28 of 41 passes for 175 yards and a touchdown in the 17-16 home loss they suffered to the Buffalo Bills in Week 1. Buffalo scored 14 unanswered points in the fourth quarter to seal the victory.

As for the new starter, Siemian spent the 2018 season as Kirk Cousins' backup with the Minnesota Vikings. Before that, he spent his first three seasons with the Denver Broncos. He got a chance as the starter, but only recorded a 13-11 record before Denver opted to trade him to Minnesota. In 26 games (24 starts), Siemian threw for 5,686 yards, 30 touchdowns and 24 interceptions. 

Falk, who will be promoted from the practice squad, was drafted by the Tennessee Titans with the "Tom Brady pick" at No. 199 overall in the 2018 NFL Draft. He was a part of the final roster cuts that year, and was quickly picked up by the Miami Dolphins. He injured his wrist and was placed on injured reserve a month later, and then waived in May. 

Bookmakers took the Monday night game off the board after the news was announced. The Browns had previously been favored by 2.5 points on the road. Westgate reopened the line at Browns -6.5, but it quickly dropped, with money coming in on the Siemian-led Jets.

Following the Monday Night Football matchup with the Browns, the Jets travel to New England to take on the Patriots. The preliminary line on that game had been Patriots -13 but will climb with Darnold out.