Former England Under-20 international Harrison, who made his debut in a Heineken Cup tie against Treviso in 2009, said: “I was surprised when I was told during training that I would be starting because I hadn’t played at all this season and I didn’t really expect to be involved. So it was quite a shock.
“But it felt great to get that first league start. You just want to play and I was very thankful to get a chance.”
The 21-year-old added: “There is a lot of experience on the pitch and that helps you relax because people are talking around you. I’ve worked with the guys in training but it is different coming into a real game, it’s quicker and you have to keep your head and remember your work from training.
“At scrum-half you have to be bossy no matter how new you are or how experienced the guys in front of you are. It is something you have to have in your game and I’ve worked on that a lot in the last few years in the senior squad.”
The 27-18 defeat, though, left Tigers still searching for a first home win of the season.
“You obviously want to win, especially in front of your home crowd,” said Harrison.
“All through the game, maybe until the last 20 minutes, I thought we were on top, especially up front, then they got away from us. It didn’t feel like we had a lot of possession in the last 20 minutes when we really needed it.
“It is frustrating, it’s hard when you’ve given your all as a team and you come out with nothing.”
Director of rugby Richard Cockerill said: “It’s obviously disappointing for Sam to finish on the losing side in his first league start but I thought he did well. He looked sharp, he was as committed as ever and I’m happy for him to have his chance.”