Caoimhín Kelleher, 26, will arrive late to the Republic of Ireland camp on Tuesday due to a medical appointment at Brentford.
Ireland will face Senegal at the Aviva Stadium on Friday before an end-of-season friendly in Luxembourg on June 10th.
Mark Flekken, Brentford’s starting custodian last season, also had a physical on Monday at Bayer Leverkusen ahead of his £8 million (€10 million) transfer to the German club.
Brentford are likely to pay Liverpool £12.5 million (€15 million) for Kelleher, with performance-related add-ons raising the transfer fee to £18 million (€21 million).
Leeds United and West Ham United were also interested in signing Kelleher but the Cork man is expected to link up with Ireland captain Nathan Collins as Brentford manager Thomas Frank attempts to improve the club’s 10th place finish in the Premier League next season.
“I think everyone knows how good Caoimhín is and what he’s achieved over the last couple of years,” said Jake O’Brien after Ireland training in Abbotstown on Monday morning. “If it goes through, it’s a great move for him, to become a number one in the Premier League.
“I think everyone know how good he is and how high his ceiling is. He can push on and do great things.
“He’s definitely up there with the best goalkeepers in the Premier League and I think next year he’ll show that.
“To go and play every week is very important and he’s more than good enough. Brentford have done well this season so it’s a club he can progress and do a lot at.”
The other 22 players picked by Ireland boss Heimir Hallgrímsson went through training before facing Senegal.
If Kelleher is unable to start on Friday or next Tuesday in Luxembourg, Bristol City’s Max O’Leary, 28, is certain to earn his maiden international cap.
Hallgrímsson has rested the majority of Irish players in the EFL Championship, including Burnley’s Josh Cullen and Middlesbrough’s Finn Azaz, as the June friendlies fall in the middle of their offseason.
On September 6, the World Cup qualification campaign begins against Hungary in Dublin.
