Head coach Schmidt this week returned to his native New Zealand following a family bereavement.
Farrell confirmed Schmidt will be back in Ireland come the weekend, but admitted it is yet to be determined which coach will take charge on Saturday.
Asked if he or Schmidt will lead Ireland on Saturday, Farrell said: “That’s up to Joe, so we’ll see.
“Joe will be back in the country soon and will be in and around the set-up at the weekend.
“Obviously it’s unfortunate circumstances. I didn’t think I’d be here reading the team out on a Thursday, because that’s Joe’s job.
“But it’s been fine, we’re following the plan we’ve always followed all the time under Joe.”
Now the combative second-rower has the chance to state his World Cup case as Ireland take on the Azzurri in their first warm-up match for Japan. Head coach Joe Schmidt is likely to select four locks for his final 31-man World Cup squad, with Devin Toner, James Ryan and Iain Henderson already nailed on.
Kleyn is battling for the likely final lock berth and will partner dependable Leinster star Toner at the Aviva Stadium this weekend.
Ireland assistant coach Andy Farrell hailed the new recruit for settling into the squad quickly.
“Everyone took to him straight away, he’s acquitted himself very well,” said Farrell.
“Hopefully we’re able to see his point of difference.
“First of all he knows he has to fit into a strategy. But he’s also, within that, got to play his game and bring his best to the table.”
Joey Carbery starts at fly-half with Johnny Sexton continuing to recover from a thumb complaint, with Leinster’s Luke McGrath at scrum-half. Munster flanker Tommy O’Donnell will win his first cap since March 2016, with Jordi Murphy slotting in at number eight.
Wing Dave Kearney features for the first time since November 2017, further underscoring Schmidt’s determination to hand out the opportunities.
Ireland team to face Italy in Dublin on Saturday: J Larmour (Leinster); A Conway (Munster), G Ringrose (Leinster), C Farrell (Munster), D Kearney (Leinster); J Carbery (Munster), L McGrath (Leinster); J McGrath, R Herring (both Ulster), A Porter, D Toner (both Leinster), J Kleyn (Munster), R Ruddock (Leinster, capt), T O’Donnell (Munster), J Murphy (Ulster). Replacements: N Scannell (Munster), C Healy (Leinster), J Ryan (Munster), I Henderson (Ulster), T Beirne (Munster), K Marmion, J Carty (both Connacht), M Haley (Munster).
George Ford discusses England’s World Cup preparations leading into a RWC warm-up game against Wales at Twickenham.
Sign up to our mailing list here and we’ll keep you up to the minute with weekly updates from the world of rugby.