Liam Williams will start at full-back for Wales in Saturday's Six Nations opener against Ireland in Cardiff after injury ruled out Leigh Halfpenny.

Cardiff's Williams, who was included in the original matchday squad, will wear the number 15 jersey.

Wales assistant coach Jonathan Humphreys said Williams is "good to go".

It is the third time in recent months that 34-year-old Halfpenny has been a late withdrawal from the Wales team.

He was named by Wayne Pivac to face both New Zealand and Australia last autumn - having made his Test return against Georgia as a replacement - only to pull out of both games shortly before kick-off.

However, head coach Warren Gatland was braced for this twist having revealed Halfpenny sat out training sessions this week with a hip complaint.

"Unfortunately, Leigh had a back spasm this morning (Thursday) and Liam will be playing," said Humphreys.

"It's more disappointing for [Leigh] as a person. He's had a couple of these recently.

"He's an unbelievable professional and an unbelievable person. He's got to pick himself up again. You feel for him that he's got to pull out at this late stage again."

Williams may not offer the same kicking option as Halfpenny but the veteran of 81 caps is a vastly experienced replacement.

He has not played for Wales since starting all three Tests on the summer tour to South Africa having missed the autumn series with a collarbone injury suffered on his Cardiff debut in September.

He remained a concern for the Six Nations after concussion on his return - against Halfpenny in a game against Scarlets - followed by a hand injury.

Humphreys said: "Liam is a great replacement to have and is good to go."

Wales have confirmed the Principality Stadium roof will be closed for the fixture.

Ireland: Keenan; Hansen, Ringrose, McCloskey, Lowe; Sexton, Gibson-Park; Porter, Sheehan, Bealham; Beirne, Ryan; O'Mahony, Van der Flier, Doris.

Replacements: Herring, Healy, O'Toole, Henderson, Conan, Murray, Byrne, Aki.

Wales: L Williams; Adams, North, Hawkins, Dyer; Biggar, T Williams; G Thomas, Owens (capt), Francis, Beard, Alun Wyn Jones, Morgan, Tipuric, Faletau.

Replacements: Baldwin, Carre, Lewis, Jenkins, Reffell, Webb, O Williams, Cuthbert.