The Norwich City captain suffered an injury during the closing stages of Tuesday night's game at Watford when a 2-2 draw hampered the Canaries chances of automatic promotion.
30-year-old Holt has become a talismanic figure for Norwich since joining from Shrewsbury in the summer of 2009, netting 43 league goals in just 79 games.
He had joined the Shrews from Nottingham Forest where his record was a respectable 20 goals in 96 league appearances, 22 of which were as a substitute.
"For the people who were asking 'could he cut it up there?' he's proved a lot of people wrong," Norwich boss Paul Lambert told BBC Radio Norfolk recently.
"I don't think he's really had a fair crack at Championship level with the teams he's been at.
"He must have played one or two games [on loan at Blackpool in 2008], that's not saying somebody can't do it in the Championship."