Baker Mayfield Caught Popping a ZYN During 'Monday Night Football'

There are many things needed on an NFL sideline to ensure players are ready to go ... water, medical tents, video tablets -- and a container of ZYNs?!?

Well, that was at least the case during the Tampa Bay Buccaneers' game against the Baltimore Ravens on "Monday Night Football" ... 'cause Baker Mayfield was spotted getting his nicotine fix on the bench.

The ESPN cameras captured Mayfield popping one of the popular pouches -- which are billed as an alternative to tobacco products -- right before the second half.

While it's hard to tell if the 29-year-old is an upper or lower-deck type of guy (meaning where the quarterback placed it in his mouth) ... the buzz didn't give Mayfield the ability to lead a miracle comeback against Lamar Jackson and the Ravens -- losing by a final score of 41-31.

Mayfield did at least put up respectable numbers by the end of the game ... going 31-45 for 370 yards with three touchdowns and two interceptions.

Now sitting at 4-3 on the season, the team suffered more than just a loss on the field -- as both star wide receivers Mike Evans and Chris Godwin went down with injuries ... the latter's being season-ending.