MADRID, Jan 19 (Reuters) - Italian striker Antonio Cassano says his goal-scoring debut was the perfect way to start his Real Madrid career and silence critics who had raised question marks over his fitness.'I couldn't have asked for a better debut,' the former AS Roma player was quoted as saying in sports daily AS on Thursday. 'I am really happy and hope that the run continues in the next few games.' The 23-year-old, who has spent his first two weeks at Real trying to lose weight and regain fitness after a muscle strain, made the most of an error from Real Betis keeper Toni Doblas to score an opportunist strike three minutes after coming on as a substitute in the King's Cup tie. Real won the quarter-final first leg 1-0. 'The fans were shouting 'fatty' at me, but I just stayed calm,' he said. 'For me the important thing was for the team to win, everything else was secondary. 'Whether I'm fat or not doesn't really matter, the good thing was that we won a very tricky game. 'It's not surprising that after a month without playing I'm not in top shape, but I will improve little by little. I'm satisfied about my fitness and felt positive about everything ... I won't take long to recover my best form.' Cassano's goal-scoring debut emulated that of Ronaldo who netted within two minutes of making his first appearance for Real when he came on as a substitute in a league match against Alaves in October 2002. The Brazilian, who scored a second before the game was over, had also been criticised for being over-weight and had to spend over a month working on his fitness after joining Real from Inter Milan.