The Team GB Olympic forward looks to have scored his last goal for the Welsh club against QPR on Saturday, with a transfer very close, according to the first team coach
Goal.com exclusively revealed on August 8 that the Premier League champions have agreed terms with the Team GB star after deciding to let winger Adam Johnson go and Swans boss Michael Laudrup confirmed on Friday that the attacker had decided not to sign a new contract.
Curtis explained to Sky Sports: "[Sinclair is] not really interested in signing a new contract and I think Man City have made a bid, so it's just a matter of time now before it happens and it's good for both parties.
"He's been terrific for us, to be fair - we've had two seasons out of him and he was superb in the Championship and virtually his goals [27 in 2010-11] got us promotion.
"And last year as well he wasn't maybe quite as effective as he was his first year - obviously it was a lot tougher opposition - but he's been absolutely magnificent.
Curtis believes the Swans will continue to push forward even if some of its top stars have left the club
"Like Joe [Allen, now of Liverpool] we wish him all the best, but as long as the club keeps pushing forward that's the main thing," Curtis said.
"It obviously gives Scott the chance to settle in at his new club and it gives us the opportunity to buy a replacement for Scott."
Sinclair scored the last of Swansea's goals in its 5-0 obliteration of QPR on the Premier League's opening day.