Sunderland manager Steve Bruce believes it is only a matter of time before a player challenges the transfer window as a restraint of trade.The Black Cats only just managed to sign striker Benjani in time on deadline day due to technical problems. [LNB]And Bruce feels that, had Benjani not been allowed to join from Manchester City, it could have damaged his career. [LNB]"I wouldn't be surprised if a player stops the window by saying it's a restriction of trade," said Bruce. [LNB]Communications problems meant the Football Association and the Premier League had to make a decision on whether or not the deal had gone through in a mad rush before Monday's 1700 GMT deadline.[LNB] Is Benjani the right man for Sunderland? Bruce added: "Take Benjani, for example. Benjani has come up here now to try to earn himself a contract. If the deal hadn't gone through, then it restricts his career, it restricts his movement. [LNB]"That's why we carry the squads we carry. They are too big and we can't keep them all happy." [LNB]Bruce was delighted to have secured the signing of Benjani on loan after deciding to allow David Healy and Daryl Murphy to join former Sunderland boss Roy Keane on loan at Ipswich. [LNB]"In the back of my mind, I knew there was a deal for Murphy and Healy and with the injuries we have had, I was juggling thinking, 'Do I let Murphy and Healy go?'" said Bruce. [LNB]"The one thing they want to do is go and play football and they weren't going to play here so I thought to myself, 'If I am going to do that, I have got to bring somebody in'. [LNB]"I wanted somebody with a bit of know-how and a bit of presence, and somebody who as been there, done it and worn the T-shirt in the Premier League, and I am delighted we got Benjani."