Iain Henderson will start Ireland's vital World Cup Pool B contest against Scotland on Saturday after being preferred at lock to James Ryan.

The other change from the win over the Springboks sees hooker Dan Sheehan take over from Ronan Kelleher.

Both Ulster second row Henderson and Leinster's Sheehan made strong impacts off the bench against the Springboks.

With Robbie Henshaw ruled out, Stuart McCloskey is named on the bench.

Ulster centre McCloskey has not featured in the World Cup so far but is preferred among the replacements to Keith Earls and Jimmy O'Brien for the Stade de France contest.

Henshaw picked up a hamstring injury in training on Tuesday and Ireland coach Andy Farrell said the Leinster centre is likely to be out for a couple of weeks.

"They want to see how things settle down and it probably takes about five days for that type of thing to happen but it looks like it could be a minimum of a couple of weeks at this stage," said Farrell.

Flanker Peter O'Mahony will earn his 100th cap in Saturday's game as he starts in the back row with Josh van der Flier and Caelan Doris.

Back row Jack Conan is in line for his first outing since damaging foot ligaments two months ago after being named in the replacements.

While Henderson and Sheehan have been drafted in, Farrell has otherwise kept faith with the players that started in the stirring 13-8 win over the world champions.

Despite that victory, the world's number one team will go into the Paris contest knowing that they will make a shock exit from the tournament if they lose and fail to earn a bonus point.

Ireland will top the group - and likely set up a mouth-watering quarter-final against New Zealand - if they avoid defeat or lose by seven points or fewer.

'It's like a last-16 match'

Captain Johnny Sexton admits Ireland's final Pool game with Scotland feels like it is a knockout match.

"We have viewed it like it is the last-16," said Sexton, who will retire after the tournament.

"We have spoken about that and that is why it is important that we get our preparation right, and we need to go out and get our performance right now."

Head coach Farrell says he is not focusing on the various permutations and his focus is on getting the win in Paris.

"It is a massive game and so important to us, to them and the travelling fans and those back home," he added.

"It is a huge game. We have Iain Henderson in our group. He is good at maths so he is across everything as far as that is concerned.

"The easiest way is to make sure we perform well and make sure we win the game outright."

Henderson got the nod ahead of Ryan, who had a "niggle" in his wrist but has recovered to take a place on the bench.

"He is fit. He had a bit of a niggle on a wrist but that is fine," Farrell said on Ryan.

"He trained the best I've seen him train in a good amount of years. He is fit and raring to go, there's no doubt."

The injury to Henshaw has opened the door for Ulster centre McCloskey to make his first appearance at the tournament from the bench.

"He has been excellent, as has everyone else who has not had as much game time," Farrell added on the 31-year-old.

"Stu has been top drawer, and the message to those guys has been that you have to be ready.

"Your attitude has got to prove that day in, day out and it certainly has as far as everyone is concerned.

"Stu is one of those. He is ready to slot in and he is raring to go."

Ireland team v Scotland

Ireland: Keenan; M Hansen, Ringrose, Aki, Lowe; Sexton (capt), Gibson-Park; Porter, Sheehan, Furlong; Beirne, Henderson; O'Mahony, Van der Flier, Doris.

Replacements: Kelleher, Kilcoyne, Bealham, Ryan, Conan, Murray, Crowley, McCloskey