Introduced to the game with Warriors trailing 32-3, Matavesi's performance helped Warriors stage a remarkable comeback, securing two bonus points on their way to a narrow 37-31 defeat.
And Hill thinks that Matavesi will relish the opportunity to start against London Irish. He said: "Josh will almost certainly start. I've been very impressed with him.
"He's a quality player. The more I see him, the more I like him. He certainly made an impact again. He scored a try, layed another one on and things just happen around him.
"I think we can see that he's a very exciting attacking player so we will probably bring him in against London Irish."
Matavesi started Warriors' opening two games of the season against Bath Rugby and Leicester Tigers and Hill was impressed with his passion.
"He is a very good signing for us. He is a young man who is very confident and has a lot of enthusiasm."
Meanwhile Hill says he is pleased with the form of Craig Gillies, who has made three substitute appearances this season.
He added: "Craig is very close to a recall. He is on top form and his attitude is superb. We have a lot of competition at lock at the moment and he's not far away.
"I've had a good chat with Craig and he wants to be in there. He comes on and he does everything you ask him to do. He's at the top of his game at the moment and he's looking fresh."