Middlesbrough's medical staff have launched an investigation as to why manager Tony Mowbray is having to do without so many players because of injury.
Defenders Andre Bikey, Seb Hines and George Friend all missed Tuesday's 3-1 defeat at Derby with hamstring problems and Mowbray wants to know if similar injuries can be avoided in the future.
He told the club's official website: "All the staff are looking into the injury position, why we have similar injuries to so many players.
"The demands and workload we place on the players and what they have achieved so far is possibly catching up with a few.
"No-one has torn a hamstring, they are all fatigue-related injuries, grade one tears and the like. They will be out for two-to-three weeks, not six-to-seven.
"We have spoken a lot about the squad this season and we keep digging into it. Just because of one result and performance like Derby doesn't mean we throw everything away."