Skip Bayless hosted Tuesday morning's episode of Undisputed alone, without Shannon Sharpe, and it was no accident ... we're told the Hall of Famer was upset with the opinionated TV host's controversial tweet sent minutes after Damar Hamlin's heart stopped during MNF.
And, TMZ Sports is told the network -- which wants Sharpe back as soon as possible -- doesn't know if he will return to work on Wednesday.
The controversy started when Bayless tweeted .