Chadwick, currently in the second of a two-month loan spell at Millwall from Everton, explained the situation in a brief statement given to the Lions' official website.
"I've had a groin problem since I've been here that needs operating on, and it's basically how long I can continue to play and postpone the operation until I need it.
"Hopefully I can get the Wigan game in, or even the end of my loan spell here, and review the situation after that. Then who knows about coming back here once that's done and I've recovered."
Chadwick will miss this Saturday's FA Cup tie against Walsall as Everton do not want the promising centre forward cup-tied.