Kelleher has been at Anfield since the summer of 2015, coming up through the Reds’ academy and making his debut for the senior team in 2019 in an EFL Cup tie.
In total, Kelleher has made nine appearances for the Reds in all competitions and the young goalkeeper’s performances impressed Republic of Ireland coach Stephen Kenny enough that he was drawn to give him his international debut in a friendly against Hungary earlier in the month.
Achterberg revealed that he spoke to Kelleher at the end of the recent campaign and told him to make sure he maintains his level, while at the same time look to improve constantly.
He complimented Kelleher for his performance against Hungary, where he kept a clean sheet, and stressed that he will always be there on hand to help and encourage the goalkeeper.
Speaking to Liverpool’s official site, Achterberg said: “I already spoke to him at the end of the season that he needs to make sure he maintains the level he has been showing and try to better it as well.
“I watched the Ireland game and he made a good debut in the second half.
“He came on and made some great saves to keep the score 0-0.
“He’s a really good guy, down to earth, works hard, and now you have to as a goalie keep creating your own hunger, intensity and keep your head on the right line.
“I’m there to help it, to talk about it and that’s what I do with anyone.
“He has been good in that way, so I can only keep encouraging and keep going.”
The past season saw Kelleher make five appearances for the Reds, which included two appearances in the Champions League, conceding just one goal against Midtjylland and keeping a clean sheet against Dutch giants Ajax.