Sydney: Lleyton Hewitt has pulled out of next week's Sydney International with a calf muscle injury and is in doubt for the Australian Open beginning January 15 in Melbourne.Just a day after Roger Rasheed quit as coach of the two-time Grand Slam champion, Hewitt's manager Justin Cohen said Saturday the 25-year-old Australian has a torn right calf muscle that required physiotherapy and rest.Asked if Hewitt was in any doubt for the season-opening Grand Slam, Cohen said: "It's hard to tell at this stage." "It's extremely minor," he added. "We're managing it and he'll have physio for the next three or four days."The injury is another major setback for the 2002 Australian Open runner-up and four-time Sydney champion who will fly to Melbourne without Rasheed and having played just 1 1-2 singles matches in almost four months.Rasheed tendered his resignation on Friday following a confrontation with Hewitt after Hewitt's surprise three-set loss to Russian Igor Kunitsyn at the Adelaide International."This is the hardest decision I've ever had to make, but one I felt I had no choice but to make," Rasheed said in a statement."Within the current environment, I don't believe it is possible for us to get the results we are looking for."His departure ends a three-year association which saw Hewitt slip from No. 1 in the world to 20. Hewitt also failed to add to his two Grand Slams _ at the 2001 U.S. Open when coached by former Australian player Darren Cahill, and Wimbledon 2002 under another former Australian player, Jason Stoltenberg.Cohen said Hewitt had yet to formalize a new coaching arrangement but it's likely Hewitt will make an announcement in the coming days, with Davis Cup coach Wally Masur a possibility."The intention will be to work with someone for the Australian Open, whether that's a short-term or a long-term situation hasn't been decided," Cohen said.