"But they are making progress and it's a case of getting them match fit now.
"We have to be careful with Owen. He played a lot of games last season for an 18-year-old, so we have to take it one step at a time with him but hopefully he'll be ready for Palace.
"It's the same with Alan. He's had surgery and is behind the others in terms of overall fitness, but he is getting there.
"Gavin played at Boston in our first pre-season friendly and did really well and, although he missed the tour, he should be OK for the start of the season."
All three players are expected to feature in Fridays friendly against Lazio at Portman Road.