Jenson Button’s victory in the Spanish Grand Prix has made him clear favourite to become the 2009 Formula One World Champion. The British driver has now scored four wins from five races and is 14 points clear of his nearest challenger. No driver has ever made such a strong start to the season without going on to win the title.

The BGP001 is definitely the car to be in right now.

However, Button’s incredible run of success is going a long way to hide the battle within Brawn between himself and Rubens Barrichello. The Brazilian is much closer to Button than the championship table lets on.

In fact, Button has only been significantly quicker than Barrichello in one race so far this year. Objects in your mirror really are closer than they appear.

The gap between Jenson and Rubens has always been small. Tiny even. In 58 races together at Honda (and now Brawn) the qualifying score between the two drivers is 30–28 in Jenson’s favour. There’s barely anything in it!

Barrichello struggled a little when he first joined Honda but once he got up to speed he was every bit a match for Button. Had Rubens started the 2006 Hungarian Grand Prix on intermediate tyres instead of extreme wets, he might have taken victory that day instead of Jenson.

Button scored more points in 2006 and 2007, but Rubens was the better of the two last year. In addition to being just a little bit quicker, the Brazilian made fewer mistakes and more effectively used the unpredictable races to his advantage.

The Brawn drivers are two very different racers, but there is little to separate them in terms of ultimate pace.

This year has been no exception.

In Melbourne, Barrichello was fastest of all in Q1 and Q2, but dropped three tenths behind Jenson in Q3 with a whisker more fuel on board. He would have gone close to the win had he not messed the start and crashed into Webber.

Rubens could have had a similarly good result a week later in Malaysia, but his race was spoiled by a gearbox grid penalty that forced him to drop back five places and qualify heavy.

The Chinese Grand Prix was another missed opportunity for Barrichello as he comfortably outqualified Button and set fastest lap during the race. A very good result was on the cards but Rubens only had three brake discs working in the early stages of the GP and he lost too much ground to make an impact.

With those dramas aside, Bahrain represented the first chance for Barrichello to have a trouble free run against his teammate.

Unfortunately for Rubens he was totally outclassed by Jenson that weekend, and was not helped by a risky three stop strategy that ended up being ruined in traffic. Button won at Sakhir whilst Barrichello finished 37 seconds behind in fifth. It is the only race this year where Jenson has clearly had the upper hand.

The Spanish Grand Prix should have been a totally different story though as it was meant to be Barrichello’s weekend.

Rubens was quick throughout practice and was actually looking so good that Jenson used some of his setup data for qualifying. Even after Button’s stunning lap in the dying seconds of Q3, Barrichello was still on track for his first win since 2004. The Brazilian drove past his teammate and Vettel at the start and built up enough of a lead to maintain his position during the first round of stops

That was then when things started to go wrong.

Both Brawn drivers planned on making three stops at the Circuit de Catalunya. It was the quicker option but would only be successful if traffic was not a factor.

As Jenson approached his first stop, one lap before Rubens, his engineers calculated that he would rejoin the circuit behind Nico Rosberg and would be held up behind the heavy Williams. Any delay would ruin his chances of making a three stop strategy work, so Button switched onto a two stopper instead.

It was a smart move and Barrichello’s engineer, Jock Clear, should have done the same. He didn’t and it cost him the win.

Barrichello was comfortably ahead of Jenson on the track, so he could afford to be a little conservative with his strategy. Although Brawn were happy to ‘split’ their drivers, it would have been better for Rubens to copy what his nearest rival was doing.

A three stop strategy was no longer ideal for Barrichello, but he still had a chance to win the race. It was supposed to be the quicker option after all. However, his second and third stints were fairly short, and combined they were only one lap longer than Button’s middle stint of 37 laps. This meant that after Rubens’ second stop, he would rejoin behind Button with roughly the same amount of fuel.

For that to have any chance of working he had to be right on Jenson’s tail, but Barrichello ended up eight seconds adrift and fell further back with tyre issues.

At Barrichello’s second stop, his mechanics would have been wise to have given him more fuel so that he had a chance to run on the soft tyres for longer at the end whilst Button was on the hards. Hindsight offers perfect vision, but it seems difficult to believe that Brawn always thought Barrichello’s strategy would work.

He was actually quite lucky to get second after all that, and has Felipe Massa to thank for holding up Vettel throughout the afternoon.

Barrichello could have really done with the win because he’s already playing catch up and needs every chance he can get to overhaul Jenson.

Monaco will be a fascinating race for the two drivers. Neither of them have ever performed consistently around the narrow streets, but Rubens has always been ahead of Jenson in their time together at Honda. With that in mind you would expect Barrichello to be the favourite.

It will be altogether different a few weeks later in Turkey where Jenson has always had the advantage, and then we move to Silverstone where Barrichello is unbeaten in the team.

It looks a lot like the pace is going to swing between the two Brawn drivers all year, and it could result in a thrilling fight for the championship.

That is of course providing team orders don’t come into play.

There was plenty of suggestion that Brawn had intentionally messed up Barrichello’s strategy to favour Button yesterday, although this situation seems highly unlikely.

Barrichello lost the race because he didn’t switch to a two stop strategy when it became clear that was the better option. In addition to that, his three stop strategy was not planned that well and it didn’t help him vault ahead of Jenson.

Ross Brawn said “I’d love to see Rubens win a race and see his crew win a race because it would be great for the team. There is no priority being given.”

What Ross said is almost certainly true.

Barrichello still has a very good chance if winning this year’s World Championship and Brawn’s management are well aware of it. There are still 120 points on offer and Rubens is in a great position to pick up a fair few of them.

It’s an incredible situation when you consider that many people, myself included, thought that Barrichello would be sitting on the sidelines this year giving advice to Bruno Senna.

Rubens might just have the last laugh, and if things start to work in his favour it could be his name on top of the Championship ladder instead of Button’s.

He really isn’t that far off.