England forced into reshuffle with Ben Morgan a doubt for Ireland Six Nations clash

The rugby gods seem determined to have their share of fun with England ahead of this weekend's hotly anticipated set-to with Ireland in Dublin, giving with one hand and taking away with the other. Stuart Lancaster, the red-rose coach, believes Manu Tuilagi will be fit to resume in midfield – the Leicester centre's confrontation with the great Brian O'Driscoll should be quite something – but is not holding his breath for good news on the Ben Morgan front.

Morgan, highly impressive at No 8 against Scotland before hobbling off with an ankle injury shortly after the interval, was still wearing a protective boot when the squad reconvened at the team base in Surrey yesterday afternoon. "We don't know for sure about Ben's prospects, but the early prognosis suggests he will struggle to be fit for Ireland," said Lancaster, who called in the fast-developing Saracens flanker Will Fraser to make up the numbers in training.

Fraser will return to his club tonight, but there is a possibility that another uncapped back-rower, the 20-year-old newcomer Billy Vunipola, will force his way on to the bench. Lancaster seems committed to running the Northampton flanker Tom Wood at No 8 in Morgan's absence, with James Haskell of Wasps filling the hole on the blind side of the scrum. This would leave a vacancy among the replacements, and while Thomas Waldrom of Leicester has recent Test experience, things may not work out as expected.

Lancaster went out of his way yesterday to talk up Vunipola, a club-mate of Haskell's at Wasps and the brother of the Saracens loose-head prop Mako Vunipola, who is fast establishing himself in England's match-day squad, even though he has yet to start an international fixture. "Billy has had an outstanding season," the coach said. "He's one of the top ball-carriers in the Premiership and when I was looking at the stats, I noticed he has beaten more defenders than any other player, which is quite something for a back-rower."

Vunipola, born in Australia to a Tongan family but resident in Britain from childhood, has been suffering from ankle problems and was having a fitness test just as Lancaster was discussing his qualities. Called into the senior squad last month as cover for the absent Leicester forward Tom Croft – the coach saw it as an opportunity to give him a taste of Test preparation – he has done precious little in training. This was of no concern to Lancaster, though. "He's been in all the team meetings and he's up to speed with what we're doing," he said. "Billy is in contention."

As the back-room staff work their way through the selection options – either Billy Twelvetrees or Brad Barritt will make way for the returning Tuilagi, with the latter a reluctant favourite, and there are further calls to be made at scrum-half and hooker – two other matters are high on the agenda. One is discipline, always an issue in the molten heat of an Ireland-England contest at Lansdowne Road; the other is the threat posed by the home side's uniquely effective "choke tackle" technique.

"We'll be playing away from home after five games at Twickenham and it will be different in a lot of ways," Lancaster said. "We'll have to be right emotionally: we'll need to play on the edge, but with composure. This is where last summer's trip to South Africa can count for us. You can prepare as much as you like, but when you go through the kinds of things we experienced against the Springboks in Johannesburg back in June, it makes you stronger.

"We'll also be working hard on addressing the choke tackle," – the Irish tactic of holding opponents off the ground, rather than taking them to the floor. "If we get our bodies in the wrong position going into contact and meet the wrong guys, it'll be turnover ball." And, he might have added, the Irish live for turnovers.