Both players were injured during the first half of City’s defeat at West Brom on Saturday, Jelavic injuring his knee and Hernandez his groin.
A scan on Jelavic’s knee cleared the top scorer of significant damage, but Hull put his recovery time at anything between three and six weeks, and a small tear to an adductor muscle means it will be at least a month before Hernandez is available.
The injuries have further depleted a squad missing Mohamed Diame, who is out of a knee brace but still without a target for his comeback six weeks after he was hurt at Everton, while Andrew Robertson (ankle) and Liam Rosenior (hamstring) are still out.
But Gaston Ramirez, initially ruled out for six weeks when he injured his groin on New Year’s Day, could make an early return for this weekend’s Super Sunday game against West Ham.
And Sone Aluko also has an outside chance of featuring at the Boleyn Ground after missing the West Brom game with a calf problem.