Ireland must bid to derail England's Grand Slam train without pivotal scrum-half Conor Murray, while boss Joe Schmidt has dropped lock Devin Toner for the first time.

British and Irish Lions star Murray has failed to recover from the "stinger" shoulder injury suffered in last week's 22-9 loss in Wales, so Kieran Marmion starts at scrum-half.

England will chase a second-successive Six Nations grand slam and world-record 19th consecutive win at the Aviva Stadium on Saturday, with Ireland opting for Iain Henderson's extra ballast at lock.

Six Nations team of the weekend - round four Show all 15 1 /15 Six Nations team of the weekend - round four Six Nations team of the weekend - round four leigh-halfpenny.jpg The full-back flourished in bringing George North into the game as he repeatedly joined the back line to give Wales an extra man in attack. He tackled well, with a memorable stop on Rob Kearney halting an Irish attack in full flow. Has put himself back into the running for the Lions berth. Six Nations team of the weekend - round four george-noth2.jpg Back to his devastating best with two tries this week. His first was a brutal display of power as he carried both Simon Zebo and Keith Earls over the try line to score, while his second was the result of a great drive from the Welsh pack. A mazy run towards the end of the victory over Ireland triggered one last attack as his side searched in vain for the bonus point. Six Nations team of the weekend - round four jonathan-joseph1.jpg A brilliant performance provided a timely reminder of what he is capable of. Three tries, each of differing styles, paved the way for England’s stunning 61-21 victory over Scotland. The first try saw Joseph display his pace and power, the second one came from dazzling footwork and the third saw him cut a lovely inside line to break cleanly from short range. Six Nations team of the weekend - round four owen-farrell.jpg After his horror show against Italy, Farrell was back to his best again to convert all but one of his kicks at goal – the one he missed was from his own half – and he was much smarter with his kicking to touch following the errors that littered his display a fortnight ago. Brought Joseph into the attack superbly, and finished the game at 10 once more. Six Nations team of the weekend - round four virimi-vakatawa.jpg A great week for the French wing as he scored a devastating try that put Italy out of the game and racked up more metres than anyone else this week, making an average of more than 10m per break. He beat eight defenders and made four clean breaks, and provided a display that proved just what a dangerous open-field runner he can be. Six Nations team of the weekend - round four george-ford.jpg Ford was able to take the fight to Scotland with the pack providing him with front-foot ball to work with. The fly-half linked up superbly with Farrell outside him, and also brought his three-quarters into the game with devastating results. Six Nations team of the weekend - round four rhys-webb.jpg A strong performance from Webb saw him create the first try for North with a smart supporting run to take an offload from Scott Williams and release a beautiful wide pass for Halfpenny to run on to. He was alert in defence and got the better of Ireland scrum-half Conor Murray in their battle for the Lions No 9 shirt. Six Nations team of the weekend - round four rob-evans.jpg A strong performance from the loosehead against an Irish scrum that until now had gotten the better of all its opponents. Carried multiple times, albeit with little success, but that took its toll on the Irish defence as it tired. Six Nations team of the weekend - round four guilhem-guirado.jpg The standout hooker this week as the French captain led by example, making an impressive 31 metres with the ball in hand and 11 tackles in defence, not to mention sealing a turnover in the process. Six Nations team of the weekend - round four rabah-slimani.jpg Joins his skipper in the front row after displacing Uini Atonio in the side and delivering much better performances. An impressive showing in the loose. Six Nations team of the weekend - round four joe-launchbury.jpg A candidate for player of the tournament. Launchbury has excelled on his return to the Test fold, and he once again led by example as he made a phenomenal 22 tackles against Scotland, as well as enjoying success with the ball in hand. Six Nations team of the weekend - round four alun-wyn-jones.jpg Return to form this week as he put his body on the line, making 18 tackles and 14 carries. He also disrupted the Irish lineout, stealing one throw on his own 5m line, but his best performance came in terms of his decision-making as he got all the big calls right. Six Nations team of the weekend - round four sam-warburton.jpg A brilliant performance in defence saw Warburton set the tone for Wales’s physical dominance over Ireland. He made more tackles than anyone else on the pitch in Cardiff, and he looks to be suited to not having the burden of the captaincy hanging over him. Six Nations team of the weekend - round four kevin-gourdon.jpg France have found their natural replacement for Thierry Dusautoir as Gourdon once again displayed his talents in the win over Italy. He carried well for more than 50 metres, and did his job in defence to slow down the Italian attack at the breakdown. Getty Six Nations team of the weekend - round four nathan-hughes.jpg Scotland made the mistake of not double-marking him, and he ran riot as a result. The Wasps No 8 appeared to send out a message that the returning Billy Vunipola would not be taking his shirt easily, and made an impressive 74 metres from 11 carries.

Head coach Schmidt has never before omitted Leinster lineout giant Toner for a pivotal Test, while Jared Payne also slots in at full-back with Rob Kearney missing through knee trouble.

"Conor Murray trained okay on Tuesday without contact," said Schmidt.

"We fitness tested him today and just felt that he wasn't going to be quite 100 per cent.

"Not that he couldn't function, just that once contact came back in and he got more bruising on top of bruising on that shoulder, we just felt that if we lost him early in the game, then you're vulnerable.

"It's a fantastic opportunity for Kieran Marmion. Iain Henderson came off the bench and did really well last week.

"So between Donnacha Ryan and Dev (Toner) we just wanted to give him an opportunity chance to start.

"It was a tight call as to how we jumbled that around, but Donnacha also played well last week. Not that Dev played badly but it was just trying to get that balance.

"So he's come in for that, and Rob Kearney has got a knee injury and is unavailable to be selected, hence Jared Payne has come in in his position.

"It probably won't be too long (for RK) but needs a bit of further investigation, and hopefully it's nothing too serious.

"He trained fully on Tuesday but was in a bit of discomfort afterwards, and he's just not fully fit to be selected."

Connacht scrum-half Marmion has 12 caps but just one start - against Canada in the autumn.

Former Leinster coach Schmidt admitted Ireland will miss Murray's "calm" and peerless direction in the heat of battle this weekend.

"You lose Conor's experience, 50-plus caps, you lose his calm; he's incredibly calm on the pitch," said Schmidt.

Kearney will miss out with a knee injury (Getty)

"He's a good foil for other players who are under pressure, because he very seldom looks like he's under pressure.

"You lose a defender who is incredibly good at organising other people and himself to make very good decisions, and then carry them through with positive action.

"His ability to control us and navigate us around the pitch, particularly with his kicking game, and the speed of his passing game.

Loading....

"His experience will leave a hole for us, we've got a combined caps with Kieran Marmion and Luke McGrath of about a dozen, as opposed to about 140 that they have in their half-backs.