Neil Etheridge will miss around six to eight weeks with a hamstring injury sustained at Wigan last weekend. City were winning 1 0 - when Etheridge went off but collapsed soon after conceding three goals.
Warnock also revealed Lee Tomlin has been poorly and gave updates on long term injured Matt Connolly, Sol Bamba and Jazz Richards.
"He's just got to rehabilitate his leg," Warnock said about Etheridge. "It's a grade three tear. Looking back, one or two of the lads have got stiff hamstrings. We did seven hours on the bus on Friday and that won't happen again.
"We left it a bit too late, we couldn't get a flight, and we all know what the M6 and M5 is like on a Friday. We will try to eliminate that in the future – that can't have helped.
"Lee Tomlin has been in bed all week with gastroenteritis, he's not done a thing," Warnock added. "Matt Connolly had that bad blood disorder that put him back last year, that's why he didn't go to Hull. He actually had an operation on his ankle as well this summer, he won't be available until October.
"Jazz (Richards) is probably a month away now after his pre-season injury. Etheridge we know is going to be a couple of months. (Sol) Bamba October, we know that. We've got one or two little things, you know, but that's why you have a squad."