Leicester Tigers scrum-half Ellis scored two tries for England Saxons in a 66-0 win over Portugal last Friday in his first game for six weeks and had been named in the team to face Ireland A on Friday.
Now Ellis is set to win his 23rd England cap after being called on to replace Harlequins scrum-half Danny Care, who has been ruled out with an ankle injury.
“I am just really gagging for a game. I can't wait to get out there,” said Ellis.
“It has been a while since I started a game for England. My fitness is really good. We made the most of my six weeks off and I trained really hard pretty much every day over Christmas.
“I worked on my conditioning, mentally I am really fresh for this time of year and I can't wait to play a game of rugby.
“I got about 65 minutes for the Saxons last week. It was a really fast game, there was hardly any kicking and it was good for my match sharpness.”
Ellis will be paired at half-back by former Tigers teammate Andy Goode, who left Welford Road in the summer for Brive.
He said: “Goodey has been playing really well and it is nice to be back involved with him.
“I have spent most of my career playing alongside him and hopefully we will click again and forge a new partnership together.”