Ferrell (right) plays the manager of a Michigan basketball team

The basketball comedy made $15.3m (�7.7m) in its opening weekend, compared with $33m (�16.6m) for his 2007 hit Blades of Glory.

Box office analysts have blamed the performance on a slow time of year and a more restrictive R certificate.

No Country For Old Men was boosted by its Oscars success, climbing to nine.

The film, which won best picture, best director and best adapted screenplay at the Oscars, saw its box office returns rise 67% on the previous weekend.

US BOX OFFICE TOP FIVE 1. Semi-Pro - $15.3m 2. Vantage Point (above) - $13m 3. Spiderwick Chronicles - $8.8m 4. The Other Boleyn Girl - $8m 5. Jumper - $7.6m Friday-Sunday. Source: Media By Numbers

Elsewhere in the new chart, historical drama The Other Boleyn Girl made its debut at number four, taking $8.3m (�4.1m).

Romantic drama Penelope, starring Scottish actor James McAvoy, Reese Witherspoon and Christina Ricci, entered at number eight.

The North American box office experienced a downturn for the third consecutive week, and is down 25% compared with the same weekend last year.

Last year, Disney film Wild Hogs captured the top spot with takings of $40m (�20m).

Ferrell's new film contains some strong language, which warranted the tougher certificate, while the majority of his previous hit releases have been given a PG-13 rating.