Deacon, who reached the landmark at a freezing cold Welford Road on Sunday, said Tigers were frustrated by the result
But he said Tigers still had a good chance of qualifying from Pool 5 when the competition resumes next month.
"We have to be positive,” said the Tigers and England lock. “We have to win our remaining two games.
“We know our next Heineken Cup game against Scarlets is going to be tough but we have to be positive and go into those two games and get the wins.
“We play Sale Sharks next and we have to focus on that. It is not all doom and gloom and we know we can improve.”
Deacon joined the likes of Geordan Murphy and Chuter in reaching 50 Heineken Cup appearances for Tigers and said his personal highlights included his European debut against Pau in 2001.
“I remember Graham Rowntree saying what a hostile place it was to play,” said Deacon. “It was tough but great to win.
“There are loads of highlights. Perpignan away the following season, the win at Thomond Park, Stade Francais here when I scored a try and then there was Llanelli (in the 2007 semi-final).
“It is a brilliant competition. I love it.”