Matthew Upson has refused to reveal whether he is free to walk out on West Ham should they suffer relegation from the Premiership.
The 27-year-old defender completed a controversial switch from Coca-Cola Championship high-fliers Birmingham on transfer deadline day, for an initial fee of £6million with a further £1.5million dependent on appearances.
The move raised eyebrows in some quarters, with the clubs facing the possibility of swapping places at the end of the season.
Upson has penned a four-and-a-half year contract at Upton Park but would not be drawn on whether - like fellow new signing Lucas Neill - the deal contains a release clause in the event of his new side's relegation.
'That's something in my contract that's quite private and I'd like to keep it that way,' Upson said.
Challenged to explain why he would abandon a promotion challenge for a relegation dogfight, Upson added: 'The simple answer to that is that I don't believe we will get relegated.
'The only real downside when I looked at the situation is the league position of the club.
'You can't disguise that - it's there.
'But I firmly believe, given the activity in January and the good base of players the club have, that won't happen.
'I guess it's my job to have an input in that as well. I'm coming here fully committed and 100% on survival. If that happens, this football club will really grow.
Upson admitted phoning David Sullivan while the Birmingham co-owner was on holiday in Barbados to discuss the possibility of joining West Ham after refusing to sign a new contract at St Andrews.
But he denied Sullivan's claims that he pleaded to be sold.
'I think the words `insisted that he release me' are a bit strong,' Upson said.
'We had a telephone conversation. I wanted to get a bit of clarification out of what was happening because I knew that he, ultimately, was the decision-maker.
'Not once did I say he must release me or demand to be released because I can't control his decision.
'I expressed a will to want to speak to West Ham if they agreed a deal.
'I always maintained my 100% commitment to Birmingham City while I was there.
'I refused two new contracts so they were aware I wouldn't sign a new deal and I think it ended up being a big decision with the offer they received and they decided it was a good offer.'
Hammers boss Alan Curbishley was resigned to missing out on Upson until a dramatic U-turn by Birmingham on Tuesday night.
'Suddenly it changed on Tuesday, it changed dramatically after our game against Liverpool and Birmingham's game against Southend,' Curbishley said.
He expressed sympathy for Blues counterpart Steve Bruce, saying: 'I've been on the receiving end of that before.
'I can understand Birmingham's decision. I can understand how unhappy they are because they've lost a quality player.'
Upson will make an immediate return to Birmingham in Saturday's Premiership trip to Aston Villa, joining Neill and Calum Davenport in a new-look defence.
Curbishley insists all three signings were necessary for the club to survive the drop, adding: 'I firmly believe we are going to get ourselves out of this.'
He also explained the rationale of allowing out-of-favour Argentina midfielder Javier Mascherano to join Liverpool - a move that is still awaiting Premier League approval.
'The boy hadn't been playing under [predecessor] Alan Pardew,' he said.
'When Liverpool lodged their interest I think we knew it wasn't all down to us as a club.
'We didn't stand in his way because he needs to be playing football.
'That's why we've allowed it to happen.'