Roberto Martinez has revealed that Bryan Oviedo is not expected to be fully fit until September.
But Darron Gibson is ready to resume training as normal following his injury.
Arouna Kone will also be back with the squad shortly after an intensive summer of rehabilitation.
Martinez said: "They are fresh, known talent which is important. It is true that we have to look after them well.
"They are so eager to get working that sometimes you have to be a little bit protective over that.
"Darron Gibson is in a very strong way and is ready to join the group straight away.
"Bryan will need a bit more individual work before he gets fully fit and probably the end of September is when we expect him to be ready.
"Arouna Kone needs a little bit more one-to-one work for a couple of weeks, then he will be able to join the group."
There had been suggestions that Oviedo would make a miraculous recovery for the World Cup and while that didn't materialise, Martinez insists there has been no setback which has delayed his return.
He explained: "Realistically, from a medical point of view, it was never a possibility (of playing in the World Cup). What made it a possibility was the way he pushed himself and the way he was working so hard - so at one stage we thought he would make it.
"Once everything settled and we were getting closer to the World Cup we realised he was a little bit behind so we slowed down a bit more to make sure we don't get any problems in the recovery.
"We never had a setback or anything other than the need for time to heal such an injury that Bryan had."