Umaga, the son of Mike and nephew of Tana Umaga, got his first call up to the England senior side in January, but hasn't played.
First-five Joe Simmonds was man of the match in Exeter's Champions Cup victory over Racing 92 last week and had another perfect day with the boot in the weekend's Premiership final win over Wasps.
However, coach Eddie Jones has included uncapped Wasps number 10 Umaga as backup to Owen Farrell, with George Ford absent through injury.
England could seal the Six Nations title with a bonus-point win against Italy this weekend if the result of France v Ireland goes their way.
England then play four games in the Autumn Nations Cup.
Former Canterbury halfback Willie Heinz is also in England's 36-man squad.