Six Nations 2014: Joe Marler's participation against Italy may be the call of the midwife

Front-rower handed deadline as partner goes into labour with Vunipola set to replace him

Rugby matches are seldom won on hairstyle alone, but there will be something important missing in Rome on Saturday when Italy take the field without the injured Martin Castrogiovanni, the majestically hirsute swamp monster of the Azzurri front row. If England's king of the extravagant coiffure, Joe Marler, misses the game as well – the Harlequin may yet be forced to put parenthood before rugby, at least for this weekend – the fashion statements will seem very tame indeed.

Marler's partner Daisy is in labour, and as the red-rose hierarchy had no clear idea of timing, they had no option but to set their in-form prop a deadline. Unless he materialises at the team hotel in time to participate in the captain's run, scheduled for early afternoon, he will be replaced by Mako Vunipola of Saracens, with the Wasps loose-head specialist Matt Mullan filling the substantial gap on the bench.

Considering the fact that England are already missing two Lions Test front-rowers in Alex Corbisiero and Dan Cole, the coaching staff seemed remarkably relaxed about this prospect. But privately they will breathe big sighs of relief if Plan A stays in place.

Marler is on as hot a streak as any of his countrymen, with the possible exception of two of his club-mates, the scrum-half Danny Care and the full-back Mike Brown, and with Castrogiovanni still suffering from a heel injury picked up during last month's defeat in France, he is the perfect man to maximise red-rose efforts at the scrum.

Italy will have Sergio Parisse, far and away their most effective operator, in the middle of the back row: the captain missed last weekend's thumping in Ireland but is fit to head up the Azzurri's bid to avoid a Six Nations whitewash that they would not have seen coming at the start of the tournament.

"When Parisse is on the field, it's as though Italy have three extra players," said Stuart Lancaster, the England head coach, on hearing the news. All the same, the visitors are expected to win by plenty, despite the narrowness of their winning margins in recent meetings with these opponents.

Whether they can hope to win by enough to bag themselves the title irrespective of what happens elsewhere is a moot point. Ireland have a 49-point advantage going into the final round of matches and if they beat the French in Paris, they will surely be crowned champions.

A one-point victory for Brian O'Driscoll and company will mean England must win by 51, and as the game in the Eternal City kicks off several hours before the one in the City of Light, the cards are very firmly stacked in favour of the men in green.

Lancaster, who confirmed a starting line-up unchanged from the one that performed so well against Wales five days ago, was keen to play the whole thing down. Yes, the presence of Manu Tuilagi among the replacements was a bonus – "He'll make an impact off the bench when he gets on," the coach said of the human bowling ball from Leicester – but almost in the same breath he insisted on some perspective. "I don't want to raise expectations that Manu will just run on to the field and score four tries," he said. "He was on from the start against Italy last year and we didn't score a try at all."

It is Lancaster's view that Italian rugby at international level has taken a leap forward in the space of a year, particularly in the attacking sphere. Certainly they have unearthed a decent back or two – the centre Michele Campagnaro and the wing Leonardo Sarto have shown enough to convince even the most sceptical of observers that the full-back Luke McLean is no longer the only man in a blue shirt capable of making a break in open field – and as a result, the Azzurri will want to play more with ball in hand. This could easily backfire on them, however, for more adventure equals more risk.

England are themselves more confident in attack and they are fit enough to make it count at the back end of the game, wherever Tuilagi ends up playing. Lancaster is highly interested in giving the outside centre a run on the wing, but if circumstances should dictate otherwise, Tuilagi will fill in for either Billy Twelvetrees or Luther Burrell in midfield.

"It depends on how the game plays out," the coach explained. "If anything happens to Twelvetrees, we could bring George Ford [the 20-year-old Bath outside-half] off the bench and shift Owen Farrell to No 12, but it's more likely that we'd bring Burrell inside and play Tuilagi alongside him.

"However, wing is definitely an option for Manu. If you look at his training times over 10 metres and 40 metres he's one of the quickest in the group, and while he would be a different kind of wing to Jonny May or Christian Wade, he'd be a lot like his brother – and he didn't do a bad job, did he?"

He could have said that again. Alesana Tuilagi also spent time at Leicester, scoring Premiership tries by the bucketload, and even though he played Test rugby for his native Samoa and therefore made relatively few appearances on the sport's biggest stages, no one questioned his status as a finisher of the very highest class. Might Manu prove every bit as good? In Rome, he may give us a clue.