And Allen, who joined Liverpool in August, believes former Swansea team-mate Williams is an excellent choice as skipper.
"I had the privilege working alongside him as captain at Swansea," Allen said. "He'll take on that role with full responsibility.
"You'll obviously have to ask Aaron on how he feels about it but he seems fine.
"He's come into this camp the same as ever looking forward to performing on Friday and obviously against Croatia away.
"Nothing will change from that point of view."
Jason Brown (Aberdeen), Lewis Price (Crystal Palace), Owain Fon Williams (Tranmere Rovers), Darcy Blake (Crystal Palace), Ben Davies (Swansea City), Jazz Richards (Swansea City), Chris Gunter (Reading), Lewin Nyatanga (Bristol City), James Wilson (Bristol City), Adam Matthews (Celtic), Sam Ricketts (Bolton Wanderers), Ashley Williams (Swansea City, capt), Joe Allen (Liverpool), Andy King (Leicester City), Joe Ledley (Celtic), Aaron Ramsey (Arsenal), David Vaughan (Sunderland), Gareth Bale (Tottenham Hotspur), Simon Church (Reading), Steve Morison, (Norwich City), Hal Robson-Kanu (Reading), Sam Vokes (Burnley).
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