HENK TEN Cate, Chelea's assistant manager, calls him "the club's best mid-season signing". No, not Nicolas Anelka, who - despite his £15 million transfer fee - scored just one league goal since arriving from Bolton. And, obviously not Branislav Ivanovic - who has yet to kick a ball in anger - either.

Nope, Chelsea's mid-season pick-me-up as it turned out has been none other than Michael Ballack. And it's Ballack who could be the difference between the two sides when Manchester United and Chelsea meet in the Champions League final this Wednesday.

Had it not been for Andriy Shevchenko and his £30m transfer fee, it's a safe bet that, right around Christmas, the big German would have been called the "forgotten man at Stamford Bridge".

After all, until December 19, he had played a grand total of zero minutes for Chelsea in the 2007-08 season. Which is not the kind of return you expect from a guy earning £130,000 a week.

Blame the ankle injury he suffered last April and the ensuing acrimony, with the club claiming he was fit to return, but Ballack, heeding the advice of his personal doctor, electing to take his time.

Jose Mourinho had counted him among his "untouchables" last season, but it's pretty obvious that, just before his departure in September, he was about as central to the Portuguese manager's plans as Tal Ben Haim (or, for that matter, Shevchenko).

In fact, according to the rumours swirling around Stamford Bridge, rather than rushing back John Terry-style, Ballack was saving himself for the European Championships.

"I had to justify myself for an operation that had taken place in an absolutely normal way, a treatment like any other, but not everyone wanted to see it that way," he says.

"That was a hard time for me because I had to fight this injury, try to get fit and all the while public claims were being made about me. They said I wasn't up for it anymore and that I felt no desire to play."

So much for that theory. Ballack has, at times, carried Chelsea in the second half of the season, as the side coped with a rash of African Nations' Cup call-ups and injuries to the likes of Terry, Frank Lampard and Petr Cech.

It's not just the fact that he scored nine goals in half a season - a Gerrardesque return for a midfielder - it's the fact that he often popped up with important ones: the brace which sunk Manchester United in the league, the icebreakers against Fenerbahce and Olympiakos in Europe, the winners against Reading and Fulham.

"It has taken me a while, but I think I've adapted to the English league," he says. "Having spent my whole career in Germany, it was always going to take a little time. And my injury didn't help either. But now I feel I'm really contributing."

Avram Grant seems to think so too. So much so that, to accommodate Ballack and Lampard in the same three-man midfield with Claude Makelele, he has often shifted Michael Essien (arguably Chelsea's best player) to right-back. Perhaps because he was rehabbing his ankle during Mourinho's acrimonious departure, the change of manager affected him less than it did many of his team-mates.

"When I joined Chelsea, I found there was an incredible bond between Mourinho and the players," he says. "That's not something you get very often... therefore, there was a great sense of belonging and, when he was gone, a lot of players exercised a kind of silent protest.

"No matter who the new manager was going to be, they wanted the old one back. It dragged on and it wasn't an easy situation for Grant."

In some ways, the appointment of Grant, criticised and derided though it might have been, did have a silver lining. It forced players to step up. The safety blanket of having Mourinho as a lightning rod was gone. Individuals had to take charge.

"I mean, we've got a lot of experienced players who take responsibility in difficult situations," he says. "We have won a lot of games by individual class, getting the decisive goals and turning games around through individual actions of players. We're clearly not yet playing the football we're capable of, but we're getting there and, just as important, we're getting results."

Grant's "modus operandi" - don't mess with Mourinho's long-established defensive schemes at one end and wait for the big guns to fire at the other - took Chelsea to within two points of the Premiership crown, to a League Cup final and now to the Champions League final. It's hard to argue with that formula.

In some ways, Ballack epitomises this. When he's in there alongside Lampard, Chelsea's build-up is far from smooth: all too often the pair end up in the same areas and make the same movements. It's not a rational midfield pairing. Yet it gives Chelsea two guys who, at any moment, can get the ball on target from 30 yards out or pop up in the box for a header or provide a viable threat on set-pieces. It's not something to be sniffed at.

What's more, without Mourinho's tactical rigor, players feel more free to take charge. Would Ballack and Drogba have argued on the pitch the way they did against Manchester United? Probably not. Most likely, Mourinho would have sorted out the relevant hierarchies before they even stepped on the pitch.

It's not an ideal solution and it's definitely not the kind of game-plan which is likely to bring success over the course of the season (which is why Chelsea had better find a Plan B next year: either bring in guys who can make a system - any system - work or bring in a manager who can make this system work with these players). But, in the short-term, Chelsea are making it work.

"I've had to wait six years to get back to the Champions League final," says Ballack. "Matches like this are why I came here in the first place. And you know what? I think beating United in the league a few weeks ago was a sign. We've beaten them, as well as Liverpool and Arsenal this season. That makes me believe that we really are the best team in England."

The good news is that they don't need to be the best team in England on Wednesday night.

They just need to be the best (or the luckiest) team in the Luzhniki Stadium for 90 minutes. And that's something which they are more than capable of doing.