The on-loan Hoops striker has endured a torrid time since joining Lierse earlier this season.
He was criticised by his manager Stanley Menzo for his condition and shape before Billy Stark then dropped him from the Scotland Under-21 squad.
Watt missed a few games for his new club after being struck down with an illness, but made his return from the bench in a Belgian League match against Charleroi.
However, he made a disastrous impact when referee Christof Virant sent him off almost immediately after coming on as a second-half sub.
Watt was adjudged to have elbowed Charleroi's Brazilian star Ederson Tormena in the head as the pair ran for a loose ball, although it seemed a harsh decision.
To make matters worse, Lierse managed to go on and win the game 2-1 after Watt had been red-carded.
Watt - who famously netted what turned out to be the winning goal against Barcelona for Celtic last year in the Champions League - has scored twice for Lierse so far in his loan spell.
But he will be banned for their next match against Leuven.