"When I arrived one of the biggest worries was not knowing about Michael's future, but since then the biggest frustration has been his niggling injuries," said Allardyce.
"He is still game short, not just in terms of pre-season, but all of last season as well. He has not played much football at all recently.
"I was actually thinking the games he played at international level at the start of the summer were very useful for him because they gave him game time. I think the same about England's friendly against Germany if he is fit to play in that. For him not being able to play in pre-season is frustrating for him and bitterly disappointing for us. He desperately needed those games, but unfortunately this thigh injury has taken longer than we thought to get better.
"It must be terrible for him because he was really looking forward to getting involved with the lads again during the pre-season games. He has done plenty of training when he has been recovering from the injury, it isn't training he is lacking, it is games and missing pre-season is a big blow for him and us."