Everton defenders Tony Hibbert and Joleon Lescott have both been hit with knee injuries.
Blues boss David Moyes explained: "Joleon's knee is getting sorted again in the summer.
"He's not missed any games for us since he arrived, but his knee does need carefully looking after. I'm nearly 100% convinced that he won't be available for England (in their friendlies against the USA and Trinidad and Tobago).
"It's not an operation, it's a series of injections to help strengthen the knee some more."
Moyes also told evertonfc.com: "Tony is going to out for probably three months.
"We are not quite sure yet whether he will need an operation. He has been for one scan and will be going for another one soon. It says a lot for his character the way he played on. He was outstanding but his knee is quite bad."
