Newcastle defender Jesus Gamez could be sidelined for six weeks after damaging his collarbone.
The 31-year-old may need an operation after falling awkwardly in the Magpies' 1-0 Sky Bet Championship defeat to Blackburn on Saturday.
Boss Rafael Benitez is waiting to discover the severity of the injury to the former Atletico Madrid right-back but admitted he could need surgery.
"We are waiting because maybe he will need an operation. The bone is a little bit high. It's not serious but you have to do it (assess) just in case," he told a press conference.
"If he has the operation it's around six weeks, but you never know because each one is different but it will be more or less this time."
Meanwhile, Benitez has bemoaned Hull's decision not to increase Newcastle's ticket allocation as the Magpies attempt to reach a first cup semi-final since 2005.
The Sky Bet Championship leaders travel to the KCOM Stadium on Tuesday evening for their EFL Cup quarter-final clash with their Premier League opponents having seen a request for more tickets rejected despite the likelihood that the 25,586-capacity ground will be barely half full.
Benitez, whose team will be backed by a travelling support of just 2,474 when the club could have sold that allocation several times over, said: "I would like to see as many of our fans as we can have there, but I can't control the policy they decide.
"Football now with a lot of TV has to be more for the fans going to the stadium, enjoying it and creating an atmosphere that will be good for the game.
"When you have an opportunity to have a lot of fans there at the stadium and you cannot do it, it's not normal. You see half the stadiums empty in Spain or 20 per cent occupied in Italy, and here when you have an opportunity and you don't do that. But you can do nothing."
The Magpies will be looking to reach the last four in a major competition for the first time since they lost 4-1 to Manchester United in the FA Cup in April 2005, and while promotion back to the top flight remains the priority, Benitez is aware of the excitement on Tyneside.
He said: "It is a motivation for us to play against a Premier League team. They are at home, so they have a bit of an advantage, but we need to go and show our levels and try to reach the semi-final.
"There are a lot of games during the season and we know we have to try to win every game."