By Martyn Herman

LONDON (Reuters) - Milos Raonic had to make do without his grasscourt guru John McEnroe but managed just fine as he overpowered Italy's Andreas Seppi 7-6(5) 6-4 6-2 to reach the Wimbledon third round on Thursday.

The Canadian sixth seed equaled the fastest serve seen at Wimbledon this year, firing down one 142mph rocket to match the delivery served by Australian Sam Groth in round one.

The fastest serve ever recorded at the All England Club was hit at 148mph by American Taylor Dent six years ago.

His second serve was not much slower either as the former semi-finalist produced an impressive show of force.

Three-times Wimbledon champion McEnroe, hired by Raonic to fine-tune his grasscourt game, was not there to witness it, however, as he had TV commentating commitments.

Raonic denied rumors that his partnership with the American had broken down, although he did confirm that he had originally approached Dutch former champion Richard Krajieck.

"I was just told about it. It's inaccurate. He was there with me this morning," Raonic told reporters of McEnroe.

"Obviously he's trying to be there as much as he can. It depends what kind of commentating schedule he gets that day," he added.

"For the first round it worked out. Today it didn't because I believe he was calling the first two matches on Centre Court."

Raonic, who plays American Jack Sock next, never allowed Seppi a foothold in the match once he had taken the first set.

At one stage he even sent down a second serve at 139mph -- all part of the strategy, according to the 25-year-old.

"So it's something that is only beneficial to me. When you get ahead in the game, you just try to sort of demotivate the other guy and use it as a mental aspect as well," he said.

(Editing by Ed Osmond)