"The atmosphere from both sides' supporters was amazing," said Deacon whose late score in front of a 31,000-strong crowd sealed the game for Tigers and sent them towards the final at Twickenham on May 20. "You could not hear some of the line-out calls because it was so loud, but it was great to play in.
"I think there has been a good atmosphere in each of the games we have played at the Walkers but it obviously helps when you are winning and get the win. When our supporters were singing Swing Low Sweet Chariot towards the end it was amazing and it really gave the boys a great lift."
Deacon's 77th-minute score from a close-range ruck put Tigers into a 33-17 lead and they defended that advantage until referee Alain Rolland blew the final whistle and allowed the players to celebrate with their supporters.
"Our biggest problem in the past has been getting close but not producing in the goods on the big day," said England international Deacon. "We made Scarlets work hard for their tries and when they did get ahead we managed to get straight back at them and we scored again.
"We have got a big squad and everybody that turns up is great for the team on the day. But the good thing is that in the changing room we are not getting carried away. We have another big game on Tuesday then we have another one on Saturday."