Montoya under pressure this weekend

The 23-year-old Columbian rookie, who enjoyed four wins within the first five races of this year's championship, looks to be under threat from Dario Franchitti.

The Scot's first win of the season last weekend in Toronto, moved him up to 106 points in the championship - just seven behind Montoya.

'The telling point in the championship will be later in the season,' Franchitti said. 'Montoya will be up at the front at every race, so we all have to stay in contention.

'Confidence-wise, this win is a big help, but that's it.'

Ex-Williams test driver Montoya had been enjoying a healthy lead, but retirements from the last two races at Road America and Toronto have eaten into his points margin.

Montoya replaced double-world champion Alex Zanardi at Chip Ganassi Racing earlier this year, when the Italian moved back to Formula One.

However, Zanardi has not performed well, and Williams bosses have voiced concerns over his lack of speed - prompting speculation Montoya would be recalled next season.