McLaren boss Ron Dennis has admitted that Juan Pablo Montoya's mysterious tennis injury was the root of the problem that led to the Colombian eventually heading off to NASCAR, unable to find a suitable F1 drive for 2007.

"The accident that damaged his shoulder was very counter-productive, it took that year out of play," Dennis told reporters at Shanghai on Sunday. "That created some tensions, but not tensions that anyone created other than the circumstances that existed as a result of that."

Although the Colombian claimed to have injured himself playing tennis, forcing him to miss the Bahrain and San Marino events. However, there was widespread speculation that the former Indy 500 winner has injured himself falling off a motocross bike.

With Fernando Alonso heading to McLaren for 2007, and little interest in him from the serious players, Montoya shocked the F1 world by revealing that he was to race in NASCAR, teaming up with his old Champ Car boss Chip Ganassi. A couple of weeks later McLaren revealed that it was letting Montoya go, though it was only recently that his contracted was fully terminated.

"He was everything you would expect him to be," said Dennis of the Colombian, who despite rare glimpses, rarely lived up to F1's expectations. "A fiery South American in and out of the car. He brought more colour to the team and Formula One."