Johnny Herbert has added his voice to that of Nico Rosberg in suggesting that Michael Schumacher could just find his eagerly-anticipated F1 return this season after three years away from the field a tougher challenge than he had been expecting.

Schumacher will rejoin the fray for the Bahrain Grand Prix curtain-raiser in Sakhir in just over two months' time with Mercedes Grand Prix, in what is being billed as the most sensational comeback in sporting history. More than 50 races have passed since the legendary German last graced the grid, and as now appears evident, when he hung up his helmet at the end of 16 seasons of arduous competition in 2006, he did so too soon.

His appetite clearly whetted by his ultimately frustrated attempt to replace injured former Ferrari team-mate Felipe Massa at the Scuderia in the wake of the Brazilian's life-threatening Hungaroring qualifying accident last summer, there are some who are tipping Schumacher - already by some margin the most successful F1 driver of all time - to simply pick up from where he left off and add to his record-breaking career statistics of seven world championship crowns, 91 grand prix victories, 154 podium finishes and a staggering 1,369 points.

As a man who raced alongside the Kerpen native at Benetton in 1994 and 1995, however, Herbert begs to differ, and contends that with high-calibre opposition of the likes of Lewis Hamilton, Jenson Button and Fernando Alonso - the drivers who have between them sewn up four of the last five drivers' titles - as well as Sebastian Vettel, Mark Webber, Massa and even his own Mercedes team-mate Rosberg, at 41 years of age now, 'Schumi' may not find it quite that easy.

"Michael is such a competitive character that I can understand him coming back with this new generation of drivers that we've got from Lewis to Vettel and even Jenson and Webber, because Mark changed massively last year, you know - really, really grew up in a very big way - and will be quite a tough cookie from this point on," the three-time grand prix-winner turned BTCC star told Radio.

"I can see him (Schumacher) and I can just imagine him looking at it - he's been out for a little bit, and maybe he stopped too early because he was still doing so well when he stopped - and thinking of coming back and doing it. Would I do it? Would other drivers do it? In some ways I probably agree with Niki Lauda, you know - why come back? There's no real reason for him to come back.

"There was that close thing we saw obviously last year with Ferrari, but the limiting factor for him is going to be his time in the car, because he has been out for that little space of time which does make a big difference. We've seen it in the past, where drivers have gone out and come back and they've struggled - Nigel [Mansell] being probably the last one. [Alain] Prost did it and he won, but he did struggle. I've always seen that where people have come back again, so it'll be interesting to see what happens."