Joey Carbery gave Ireland a World Cup injury scare after he was stretchered off during their warm-up game against Italy.
The fly-half hurt his ankle in the 50th minute while tackling Italy's No 8 Jimmy Tuivaiti and was immediately replaced by Jack Carty.
"He has an ankle sprain," Ireland head coach Joe Schmidt told RTE after the 29-10 win. "There's no fracture so that's a promising first sign.
"We're probably going to have to wait 48 hours to see whether he needs a scan. If he does we'd need to let the swelling go down a bit.
"There's a bit of swelling but it's not too bad. Fingers crossed at this stage.
"We'd be hopeful it's not going to be too bad."
Carbery scored Ireland's first try against the Azzurri and also kicked two conversions in his first start since the win over USA in November last year.
The 23-year-old endured a frustrating end to last season after suffering a hamstring injury while in Ireland's Six Nations camp and didn't return until Munster's final game of the campaign when they were beaten by his former side Leinster in the PRO14 semi-finals.
Ireland play three more games before travelling to Japan. They face England at Twickenham on August 24, live on Sky Sports, before back-to-back fixtures against Wales on August 31 and September 7 respectively.
Ireland take on Scotland in Yokahama in their World Cup Pool A opener on September 22.