Following 14 months on the sidelines with a horror knee and ankle injury, the teen is back in action for the U23s.
Critchley told the Liverpool Echo: “After over a year out, Rhian has had 70 minutes against Leicester and then another 70 minutes against Blackburn.
“Hopefully he can keep building on his fitness. The training is going to be important for him over the next few weeks.
“Pre-season will be key time for him. Fingers crossed he can build up his rhythm and his momentum.
“We can't expect too much from him too soon. Hopefully next season we'll see more of what we know he's capable of.
“We saw last summer in the States that the likes of Rafa [Camacho], Curtis [Jones] and Ben [Woodburn] got opportunities.
“Our players are always well aware of that. They need to make sure they look after themselves over the summer and follow their fitness programmes so they're able to hit the ground running in July."