He said: "What we have tried for hasn't materialised. It is extremely frustrating.
"We have to see if can bring a new player or two. For the moment, though, it is time to focus on the team again and make sure the players are ready.
"We have to give the lads who are here all the service they need to make sure they stay fit, stay motivated and stay on top of their game.
"We have a difficult period coming up and we do not want to lose the confidence we have built up over the season."
Meanwhile, Sam Allardyce has admitted that Fabrice Fernandes is up for sale this month as he looks to free up funds for other players.