First choice last season under Chris Hughton, Shane Duffy has been more peripheral for Brighton this season.
Manager Graham Potter has used a back-three predominantly. But Ireland centre-back Duffy has only started one of the last three matches.
Former Ireland defender Gary Breen gave his take on the situation at the London Stadium after our live Off The Ball commentary of their victory over Manchester United.
"It's a challenge for Shane," he admitted.
"And if I think of all of the challenges that have been put in front of that young man, he's taken them on - he really has.
"You think about the bad injury he got; gets into the Ireland squad at a time when you're thinking he's just making his mark. Instant impact! Similar in terms of what he did at Brighton.
"He goes into the Premier League and does that again. So this is another challenge."
Breen believes Duffy will meet the challenge of breaking back into the Brighton team head-on.
"But he may well look at the scenario and think, 'No matter how well I play, I'm not going to get the nod'.
"And effectively, if they're playing three centre-halves, Brighton, as they are doing in contrast to two last year, at the moment he's four choice.
"Now, he may well have a decision to make. But if you're asking me if he's the type who's going to take that challenge on and say, 'I'm going to prove you wrong', I'd say absolutely he is.
"And he's been magnificent for Ireland. Although he may not be getting his game, not for one moment will Mick McCarthy be worried about that.
"He'll be nailed on to start Ireland's games."
On why Shane Duffy has lost his Brighton place, Breen discussed how his attributes match-up with Brighton's new philosophy.