Ex-Ireland hooker Bernard Jackman says Johnny Sexton is hopeful of being fit for the start of the Six Nations.

The Ireland captain required a "procedure" on a cheekbone injury sustained in Leinster's United Rugby Championship win over Connacht.

"Sexton is quite confident he is going to be back for the first round," Jackman said after speaking to the 37-year-old Ireland fly-half.

Jackman says he spoke to Sexton 24 hours after his operation at The RDS, where the Irish captain accepted his Honorary Life Membership award.

"He didn't have to get wired - it was a simpler procedure than we all feared," added Jackman.

"He is due back in four weeks so should be back for the first game against Wales which will be a huge boost for Ireland - he is delighted."

The match in Cardiff will herald the return of Warren Gatland as Wales coach after he was named as the replacement for Wayne Pivac.

"Wales away in round one with [Warren] Gatland coming back in has now become a dangerous fixture. More dangerous than before Gatland came in as Wales weren't overly consistent. So there will be a big lift in Wales' performance."

"If Ireland were to lose that first game then it would throw the Grand Slam out of the picture and it is very hard to gain momentum.

"If he [Sexton] is fit he plays. He is always someone who has been able to do really well after a break. There are certain players you want to see them have a game before they play a big game.

"But Johnny has shown whether it is two weeks or four weeks or more he is able to hit the right notes and because he is a key man for Ireland it is important he starts.

"Then see how the tournament goes to give someone else a chance. I think Ireland want to try and win a Six Nations and our best chance of winning a Six Nations is if Sexton plays."

Jackman, who won nine caps for Ireland, believes Munster's Joey Carbery is still in prime position to be the first-choice cover for the Leinster fly-half, despite his injury in November which saw him miss the final autumn Series win over Australia.

Carbery's provincial team-mate Jack Crowley started the game and impressed before Ross Byrne replaced him to kick the winning goal in the 13-10 victory.

He added: "I still think Joey [Carbery] is the number one back-up. The interesting thing will be Crowley over Byrne. Byrne came out of the wilderness against Australia but showed his mentality and big game temperament.

"Since then Crowley has been getting a lot of game time but in a mixture of 10 and12. Anybody who works with him rates him incredibly highly. I have a feeling he is going to possibly be third choice 10 going towards the World Cup.

"However over the next month with Johnny [Sexton] being out it gives Ross Byrne an unbelievable chance to lay down a marker as well with big games in Europe. At Munster you would imagine Joey would be at 10 and Jack at 12.

"A lot could change over the next month but Crowley is somebody who everybody who works with him says he has incredible ability and temperament to go on and do great things."

Ireland's second Six Nations game is against last season's Grand Slam winners France at the Aviva Stadium on 11 February, the first of two home games before they welcome England in the final round on 18 March.

"A Grand Slam or title would be great but if we are to win four out of five and perform well in the game we lost I don't think that would be a big blow," the former European Cup winner continued.

"I think England are also going to get better so that game is now tough. France as always will be incredibly hard to beat but the fact we have both of them at home this year improves our chances of winning the trophy."