Mr Saunders wrote the note to the Chelsea defender Paul Elliott, injured by his tackle during a game against Liverpool at Anfield in September 1992.
The message, written a few months after the game, said: 'Just a note to wish you luck in your recovery. Nobody was more disappointed than me. I can promise you there was no malice intended. Hope you are kicking me soon.'
Mr Elliott, 30, is suing Mr Saunders, now with Aston Villa, and his former club Liverpool for negligence and damages that could run into millions of pounds. It is seen as a test case as it is the first involving two high-profile players in a dispute over an injury on the pitch.
Mr Saunders, who denies liability, was playing his last game for Liverpool before his pounds 2.4m move to Aston Villa. He said he jumped at the ball in the tackle because he feared a serious injury as Paul Elliott jumped in. 'I thought I was in big trouble,' he said. 'As soon as he took off I knew there was going to be a collision. Instinct told me to get my feet off the floor. I aimed to land on the ball and I believe I touched it.' He said there was no other option than to go for the ball. He had to be careful about making sliding tackles because when he was 18 he had suffered a serious knee injury, similar to Mr Elliott's.
After the challenge, Mr Saunders said he saw Mr Elliott in agony on the pitch and noticed stud marks on his knee. But there was no antagonism from Chelsea players.
Earlier, the hearing was told in a statement by the former Arsenal manager Bertie Mee that Mr Saunders had deliberately committed the most dangerous type of tackle in football. 'It was a coward's tackle in that he knew what he was doing,' he said.
A former Liverpool midfield player from the early 1970s, Brian Hall, disagreed.
He said: 'The defender had committed himself to a tackle with the simple view of stopping the forward reaching the ball.' Mr Saunders could not have avoided the challenge.
Augustus Ullstein, QC, representing Elliott, said Mr Saunders had previously elbowed a player in the face during an FA Cup tie. Mr Saunders said it was retaliation after the player had knocked out his front tooth.
The case continues today.