Ian Crook resigned Sunday as coach of Sydney FC hours after the team's fourth loss in six matches to start the A-League season, citing health concerns for his decision and surprising the club's hierarchy.

Sydney FC said Sunday that assistant coach Steve Corica would take over on an interim basis, the team's seventh coach since its inception in 2005.

"I just felt that it's started to affect me and probably my health. I haven't enjoyed it for a few weeks, if the truth be known,'' Crook said at a media conference.

On Saturday, Crook substituted star recruit Alessandro Del Piero in the 66th minute with Sydney leading the Melbourne Victory 2-0. But the Victory scored a comeback 3-2 win, and Crook later had a verbal altercation with Sydney fans who complained to him on the sideline about Del Piero's removal.

He said later it was always planned to substitute Del Piero, the former Italy and Juventus star who had suffered from hamstring tightness and didn't play in Sydney's 7-2 loss last week to Central Coast.

"I've felt like it's been a burden, a constant burden and once something gets like that, that then obviously has a flipside where it starts affecting my family,'' Crook added Sunday.

"I'm sure they will (ask if I was) pushed - the answer 100 percent `no'. This is 100 percent my decision. I could have stuck around for another four, five, six, 10 weeks but it wouldn't have given somebody else time and I wouldn't have changed the way I felt.''

Sydney FC chief executive Tony Pignata, who was credited with getting Del Piero to move to Australia on a two-year deal, said the decision was a surprise.

"I got a text message this morning at 1:30 a.m. from Ian about calling a meeting with myself and (football director) Gary Cole this morning at 8:00 a.m.,'' Pignata said.

"Had a quick chat with him last night, I was still up watching the game and we met together at the training center at 8:00 a.m. where Ian tendered his resignation and it was quite surprising. I tried to talk Ian out of it but he was quite adamant.''

The 49-year-old Crook began his playing career with Tottenham Hotspur before making 418 appearances for Norwich City.

Crook replaced Vitezslav Lavicka at Sydney FC and was assistant coach at the club under Pierre Littbarski when Sydney won the inaugural A-League title in 2005-06.

He moved to Japan the next season and had other stints in Australia and England before returning to Sydney in 2010.

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