There had only been one retirement by this stage, as Zsolt Baumgartner spun his Minardi out of last place on lap 18, but problems were already beginning to manifest themselves in the middle order.
Montoya, having made his tardy start, found that he could keep Barrichello at bay until his pit-stop, but called for more front wing and attention to his brakes before resuming in the lower points places. Button had struggled to make any ground in the early stages, moving up to 13th past Cristiano da Matta on lap three, but then finding himself back down in 14th after the pit-stops as the two-stop runners gained time on him. The two McLarens were already keeping the Briton company, however, and, although both would finish the race, neither would score points, underlining the Woking team's current malaise.
Seven laps after the two Ferraris had completed their first round of stops, Schumacher held a 22secs advantage over his team-mate, and the dye appeared to be cast when the German made his second stop. This was where Barrichello had to get the hammer down and ensure that the world champion emerged behind him with a stop apiece to complete, but it was not to be. As Schumacher got back up to speed at pit exit, Barrichello was still coming down the main straight, and had to settle for second.
Behind the two red missiles, Trulli continued to hold third place, now ahead of Renault colleague Alonso, who had disposed of Sato during the second round of pit-stops, with Giancarlo Fisichella disputing sixth with Montoya courtesy of his different strategy. The Colombian, meanwhile, had called for more adjustments to his front wing as he continued to struggle with the Williams, but had a comfortable gap back to team-mate Ralf Schumacher, who had the two-stopping Sauber of Felipe Massa for company.
If Olivier Panis had seen any hope of a points finish recede following an average opening stint, it disappeared completely when he was adjudged to have exceeded the pit speed limit and was called in for a drive-thru' penalty. That left the Frenchman down among the McLarens, but his TF104 was not long for the race, eventually calling it a day at half-distance with hydraulic failure. Joining him on the sidelines at roughly the same point was the second Minardi of Gianmaria Bruni, which pulled off with 31 tours under its belt, and Nick Heidfeld, whose Jordan cried enough with a gearbox malady.
Despite the expectation that it would run like clockwork - as it has done for more than a season - Schumacher's F2004 suddenly began to sound like a candidate for the retirement list, passing the pits and causing the Ferrari crew to listen intently to its engine note. The car was definitely sounding off-song, but technical director Ross Brawn quickly decided that the culprit was nothing more serious - at this point - than a cracked exhaust, and simply told his star driver to turn down the wick. Schumacher had a five-second advantage over Barrichello and, problem or not, the gap did not close.
Things then got worse for Barrichello's hopes of catching and passing his team-mate for, at his final stop, the Brazilian was amazed to find that the team did not have his tyres ready and waiting for him. Vital seconds were lost as the mechanics frantically unwrapped the new rubber, dropping the second Ferrari far enough behind its counterpart to ensure that Schumacher could keep his reduced pace to the finish.
Montoya pitted at the same time as his South American friend, rejoining as normal but quickly returning. This time, the stop was more dramatic, as Montoya bowled his front jackman over as the Williams' lack of brakes took over. Retirement was inevitable for the Colombian, who later admitted that he had been fearing a poor result at a track he felt did not suit the strengths of the FW26. Montoya's retirement was not the last, with Christian Klien dropping out with a throttle problem on the second Jaguar and Giorgio Pantano completing a miserable day for Jordan as he parked up with hydraulic failure.
Although Button was able to take advantage of Montoya's demise to inch closer to the points, he had to dispose of Mass's Sauber before claiming eighth place and the had reason to thank the gap he built up over the Brazilian as his BAR went sick in the closing stages, forcing him to slow in the run to the flag. The problem saw the Briton lapped by the leaders, but he managed to notch up one more point towards a fast fading title challenge.
Ahead of the Honda-powered driver, Giancarlo Fisichella echoed Barrichello's belief that a two-stop strategy would work around the Circuit de Catalunya, claiming his first points of the year, and the first of his association with Sauber, but could do little to fend off Ralf Schumacher, who took sixth after a relatively quiet race. Fifth fell to Sato, who put in a clean drive but could not capitalise on his third grid slot when the Renaults proved a little too strong for the BAR.