1. Denzel Mims, WR, NY Jets
There was never going to be anyone else at the top of this list. Denzel Mims was the most disappointing Jets player in 2021, and it isn't particularly close.
Where to begin with Mims? The 2020 second-round pick flashed promise as a rookie and was expected to compete for a starting job in the spring/summer of 2021, but it soon became apparent that the new coaching staff didn't hold him in as high of regard.
Mims found himself playing with the backups in training camp and was buried on the depth chart to begin the season. He would eventually get his opportunities, and that's when it became painfully apparent to everyone why he was stuck so far down on the depth chart.
You could argue that there was no more ineffective player on the Jets' roster in 2021 than Mims. Despite receiving ample playing time down the stretch and playing over 25 percent of offensive snaps, Mims finished with just eight catches for 133 yards.
He went well over 100 snaps without recording a catch which feels almost impossible given what the Jets were working with at wide receiver late in the year. On top of that, his penalty-to-target ratio was among the highest in football.
Mims finished with the same number of penalties (five) as first downs. He would run the wrong routes, make boneheaded mental errors, and struggle to separate. Of 133 qualified wide receivers, PFF ranked Mims 132nd.
Not only did Denzel Mims play himself out of a starting job, but he's very likely played himself out of a roster spot altogether. And for that reason, no player had a more disappointing 2021 season than he did.