Sunderland midfielder Carlos Edwards says the team were surprised by manager Roy Keane's decision to resign.Keane, 37, left the Wearside club on Thursday having been in charge at the Stadium of Light for 27 months.Edwards told BBC Radio 5 Live: "The players still had full confidence in him. I went to work thinking it was going to be normal but it wasn't to be."We just have to get our heads down and continue to start winning games and push ourselves back up the table."Edwards also played down suggestions Keane had fallen out with players."Managers are going to have run-ins with any players and you will find that in any club."But to say some of the players didn't want to play for him, I'm not going to say that."Some players are always going to be unhappy about not playing, it's up to the players at the end of the day to prove him wrong."Premier League managers Martin O'Neill and Steve Bruce expressed their disappointment at Keane's early departure.Aston Villa boss O'Neill said: "I think he has done wonderfully well at Sunderland at the start of his managerial career."I'm as disappointed to hear he has left as when I heard that Jose Mourinho had left Chelsea. That's the sort of impact Roy Keane has had on football."While Bruce, Wigan manager and Keane's team-mate at Manchester United from 1993-96, told BBC Radio 5 Live: "Football is a better place when Roy is in it."I hope it's not too long before we see him back. I don't think it will be long before he is back in somewhere. I wish him well because I like him, I've always admired him as a player."He's a great football person, it beats him up when he loses. I hope that he takes a break and comes back, which I'm sure he will do."Keane took over at the Stadium of Light on 28 August 2006 with Sunderland bottom of the Championship having lost their opening four games following relegation from the Premier League.The 37-year-old former Republic of Ireland international guided them to the top of the table and they won the league by two points from Bruce's Birmingham. Keane's first Premier League season was mixed yet they retained their status by finishing three points clear of the drop zone in 15th.But Sunderland have struggled this term, winning four of their opening 15 games, losing five of their last six and slipping to 18th."If it is his decision there must be reasons why," said Bruce. "When I last spoke to him he was thoroughly enjoying it, enjoying the challenge and all parts of the job."When he went there they were in turmoil - bottom of the Championship and without a win."It needed a big personality with a big presence to walk in and give it a shake-up and boy did he give it a shake-up."Once you get into the Premier League the focus is on you and more often than not you're playing against great, great teams who can beat you and it's difficult."He might have genuinely though he had taken them as far as he could."Source: BBC