RIO DE JANEIRO, Sept. 13 (Xinhua) -- Brazilian driver Felipe Massa has described Ferrari teammate Fernando Alonso as the toughest opponent of his 10-year Formula One career.

"I've always had strong teammates but in the past few years the challenge has been even greater," Massa said in a video interview published on Ferrari's website on Thursday.

"He (Alonso) is the most difficult driver I have come up against. Lewis Hamilton has also been a strong competitor, as has Kimi Raikkonen and Michael Schumacher."

Massa and Alonso, both 31, have been teammates since the Spaniard's move to Ferrari from Renault in 2010.

Two-time world champion Alonso is currently leading the F1 standings with 179 points, 37 ahead of second placed Hamilton (McLaren-Mercedes). Massa is 10th overall with 47 points.

The next Grand Prix is in Singapore on September 23.