Doctor Roberts is prepared to dish out the medicine

Jamie Roberts has two sets of finals on his mind, and if he gets his wish the one back home will be delayed as long as possible by the other here at the World Cup. "I've got my finals to qualify from Cardiff Medical School in January 2013," said the Wales centre.

"As soon as I get home I'll be on the wards and knuckling down for 14 or 15 months' part-time study while I'm playing for the Cardiff Blues. It has gone on the back burner for this tournament and I've missed it, but if we get to the quarter-finals and hopefully further, I'm happy to wait a bit longer."

The popular diagnosis of his efforts against South Africa (defeat by one point) and Samoa – a crucial 17-10 victory – is that in his clattering charges and fringe defence he has rediscovered his player-of-the-series form of the Lions' 2009 tour to South Africa.

Roberts, who will be rested for the meeting with Namibia in New Plymouth tomorrow but is bound to return for their pool decider against Fiji on Sunday, said: "It kind of implies I've been terrible the last two years." But he admitted: "What I did do was to set myself targets three or four months ago to get myself as fit as I can and get over some niggly injuries. I am feeling fitter than for a long time but that only takes you so far.

"It's the buzz of playing these big games that gets the adrenalin flowing. You may only play one World Cup in a lifetime, so make the most of it. Performing when it matters is what counts."

Rob Howley, Wales's attack coach and an assistant on that Lions tour, said "depending on the individual" it may take "18 months or even two years to recover a level after the ecstasy of a trip like that".

No World Cup team are fielding waifs in the midfield and the lack of Gavin Henson and the retired Tom Shanklin has left Roberts dovetailing with Jonathan Davies as the first-choice, 34-stones-plus pairing.

Samoa's Seilala Mapusua was left with a headache after a collision with Roberts, and a judo-style grapple took care of the equally enormous Alesana Tuilagi. Fiji present a similar challenge. "Against the Islander teams, you can't afford to play loosely," he says. "Sometimes that does mean being confrontational, playing direct rugby, matching them physically, trying to dominate them. "

The coach Warren Gatland will decide on his first-choice fly-half after Stephen Jones wins his record 101st cap tomorrow. The experienced Jones has been waylaid by a calf injury but the 24-year-old Rhys Priestland has been impressive. The power game is non-negotiable, but Wales will have to do without the dainty touches of Shane Williams after the winger was found to have torn a muscle in his thigh.

Wales v Namibia is on ITV1 tomorrow morning, kick-off 7.30am