Avram Grant believes he has proved to the Chelsea fans that he is the master of the tactical substitution.

The 52-year-old Israeli coach was abused by a section of the Chelsea fans earlier this season and taunted with cries of 'You don't know what you're doing' when they disagreed with his substitutions in big games.

But victories over Arsenal, Liverpool and Manchester United were achieved with tactical switches and the addition of other players at the right time and Grant insists he will not be afraid to do the same against United in next week's Champions League final in Moscow.

He said: "In big games, changing the players or the system at the right time is one of the best ways to win the game when you know your opponents so well."

Meanwhile, the Football Association have written to Grant to ask him to explain his remarks about referee Steve Bennett.

Grant called Bennett's integrity into question after Manchester United's 2-0 win at Wigan last Sunday earned a tenth Premier League title for Sir Alex Ferguson.

Chelsea, level on points with United before kick-off, could only draw at home with Bolton.

But Bennett came under fire for not awarding the home side a penalty for handball and then opting not to send off Paul Scholes for a second bookable offence when he fouled Wilson Palacios.

At his Champions League media conference on Wednesday Grant said: "In England there are very good referees, but there are some - a few that you can influence, like you saw.

"I think in our game against Manchester United at Old Trafford, the referee (Mike Dean) influenced the result for sure. We know that.

"I think the red card for Mikel John Obi in that game should not have been a red card, I think that Paul Scholes should have had a red card on Sunday and Wigan a penalty also."