The 22-year-old replaced Liverpool’s injured No.1 for last week’s meeting with AFC Ajax at Anfield and delivered an assured display while helping his team to a 1-0 win that booked their spot in the competition’s last 16.
Kelleher made several excellent saves throughout the 90 minutes, with perhaps the best coming in the closing stages when he denied Klaas-Jan Huntelaar from point-blank range.
“It was just a bit of an instinctive reaction save, to be honest,” he recalled, ahead of Wednesday’s final Group D match against FC Midtjylland.
“He was that close in I just tried to get anything that I could on it and luckily I was able to get it away to safety. It was a nice moment to make that save.
“Then after the game, for the manager to come up to me - it was a nice moment for me. I wasn’t expecting it so it was a nice moment.
“My phone was buzzing for about three days after the game! Just [with messages] from friends, from former coaches, family, everyone really.
“Alisson texted me as well just to say ‘well done’ and that he was proud of me and stuff. All the messages were nice and supportive so it was really nice to get all of them.
“It’s been a decent week for me! What can I say, two debuts in one week was a bit of a mad one so it’s been a good week.”
Kelleher followed that performance up with another fine display as the Reds beat Wolverhampton Wanderers 4-0 in the Premier League on Sunday.
“Definitely on the weekend I felt more comfortable after playing midweek,” he continued.
“I think the more games I play, the more comfortable I’m feeling.”