Clark, who has been in charge at Birmingham since the start of the season, fumed that the towering forward owed the club and the fans significantly more effort.
"[Zigic] won't be involved," he told reporters ahead of the game against the Championship's fourth-placed side. "I witnessed possibly the worst training session, in terms of a professional footballer, I've ever come across yesterday.
|12/5||Birmingham City are 12/5 with Bet365 to fail to score against Watford|
"He was starting in the team and he knew that because we had done our preparation on Thursday about how we were going to approach the game, both with and without the ball.”
Zigic arrived at the Midlands club from Valencia in 2010 for a £6 million fee and is reportedly costing the club a further £60,000-a-week in wages.
"This has been coming," Clark continued. "Whether he is angry because he has not started enough games in recent weeks, that could be valid. But does that mean he can down tools and not try? The fans and the football club deserve more than that.
"He is a very well-paid guy and you've got to earn that and what he dished up yesterday was what, since I left school at 16 and have been in professional football, not technically or tactically, the worst training session I have ever seen."
|"What he dished up [on Thursday] was what, since I left school at 16 and have been in professional football, the worst training session I have seen"
- Lee Clark on Nikola Zigic
Clark has not started the Serbia international since the 16th-placed club's 3-1 away defeat to Bolton in December, a match in which Zigic opened the scoring but was later shown a red card.
However, the 40-year-old manager remains clear that the forward can still work his way back into the side, despite this latest setback.
"That [his future at the club] is up to Nikola," he concluded. "I haven't had a bust-up with him. There has been no shouting match. It is up to him."