Stewart stood out in both games against Slaven Bilic's side, and gave a good account of himself in the games Exeter City in the third round of the competition.
The 22-year-old told the official Liverpool website: "I've waited a very long time for [this], so it's a bit of relief to finally show what I can do.
"Most of my career, the games I've played well in have been against younger players and players my age.
"It's nice to prove to myself I can cope with the Premier League players and do well against them.
"It makes it much more competitive and I think I thrive in competitive situations. When a lot of players come back [to fitness], we need to fight more, and I think that's why I'm going to improve."
Certainly this spell of games seems to have given Stewart a lot of confidence, and has given manager Jurgen Klopp some food for thought if there were to be a shortage of midfielders between now and the end of the season.
He signed a new deal with the Reds in the summer before making a loan move to Swindon Town which didn't work out for him as he barely played - though there was no indication on how long he has left on this deal from the Liverpool Echo report back in July.
If it isn't a case of a future of first team football at Liverpool for Stewart then he has certainly put himself in the shop window over the last couple of games.
He hasn't looked out of place, not been afraid throw himself into challenges - or get back up straight away when he has been on the end of a potentially bad one.
Given how the Reds' league campaign has gone so far, with the side way out of the running for the Champions League places, it will be interesting to see if Klopp gives the likes of Stewart a go in that environment as he assesses his squad ahead of the summer - when you can bank on the Reds having a busy transfer window.