The midfielder played at the World Cup, scoring in his side's 2-0 win over Chile in the group stages, and Adams said the 24-year-old would inevitably be in demand.
Fer got married after the World Cup and has been away on honeymoon, but is expected back at Carrow Road on Monday. He has three years left to run on the four-year deal he signed when he joined from FC Twente last summer.
"He’s just played in the World Cup, he scored a goal and he’s going to be in demand from bigger and more wealthy teams," Adams told Sky Sports News after watching his side draw 2-2 with Celta Vigo in a Carrow Road pre-season friendly on Friday night.
"Obviously with our relegation last season we’re going to be at the mercy of that.
"I’ve said many times I’d love to keep them all but we have to be realistic. If it happens, it happens, if it doesn’t I’d love for him to be playing all season with us.
"I’m not resigned to losing him. I hope he stays here, but you’ve got to be realistic.
"At this moment he’s a Norwich City player. I’m keeping my fingers crossed he will be but at the same time we’ve got to be realistic."
Queens Park Rangers boss Harry Redknapp has confirmed he would like to bring Fer - who scored four goals in 32 appearances for the Canaries last season - to Loftus Road, while Southampton have also been linked with a move.
"He's a player we like but I don't know where that one is at the moment," Redknapp told Sky Sports News earlier this week.
"It's been ongoing for a while but there are other people as well that we are looking at."
Norwich kick off their Championship campaign against newly promoted Wolves on 10 August, a match being screen live on Sky Sports 1.