Replacing Felipe Anderson in stoppage-time, the 20-year-old midfielder made his first Premier League appearance.
"I've played with Grady since the Under-16s and he's such an amazing talent," says Rice.
"He loves taking on defenders one v one. He's so quick, so sharp.
"I don't like coming up against him in training. When he gets more chances in the Premier League, he's going to show everyone what he can do."
Diangana adds: "I found out a few hours before that I was going to make the bench, so it was a surprise and I was really happy.
"I feel very honoured to have an appearance in the Premier League, and hopefully there are more to come now."
Diangana, whose second top-flight match was a 50-minute outing against Tottenham Hotspur on Saturday, received his Premier League Debut Ball along with Rice and Ryan Fredericks, to mark his first appearance in the competition.
"It was a wide awakening," he says. "It doesn't get much tougher for your first game than going to Anfield. It was a steep learning curve straight away but I enjoyed the experience.
"You want to play against the best players, see where you're at and test yourself at the highest level.
"I learned more in those three or four games I played in the Premier League than I probably have in the last four years of my career."