Indian Wells: Roger Federer eased imperiously past Juan Martin Del Potro 6-3, 6-2 in the quarter-finals of the ATP tournament on Friday but it was the first game of the match that captured the most attention.   

Federer finally held serve after saving two break points in a game that lasted 11 minutes and involved heated controversy after the Hawk-Eye ball tracking system failed to work after a challenge by Del Potro.   

On the sixth deuce, a Federer first serve was ruled in by the line judge though the Swiss immediately prepared for a second serve.   

When Del Potro's challenge came to nothing, the disgruntled ninth seed argued with the chair umpire while motioning with his fingers that the ball had bounced at least four inches wide.   

"There was a problem with that call," Argentina's Del Potro, the ninth seed, told reporters. "It was clear out and the machine doesn't work. The chair umpire told me he made a mistake.   

"After that, I was not concentrating in the match and Roger was playing better, taking all his opportunities. I don't feel comfortable playing the match, but that was my problem. Roger made his job, and he's a good winner."   

In a statement, the ATP Tour said: "If Hawk-Eye does not have data, as per ATP rules, the original call stands. We understand there was a loss of an internet connection and the data could not be provided."   

Federer also felt his first serve had landed wide.   

"I thought the ball was out, and that was it, basically," the 30-year-old Swiss said. "And then you just go with the call of the umpire and you sort of move on with it.   

"You have these bad calls from time to time. You move on. There's a good call, bad call, the worst that can happen is you run out of challenges and the umpire then misses everything and the linespeople too."        

Consecutive Titles   

Federer, who won three consecutive titles at Indian Wells from 2004, held serve on the next point when his opponent's backhand service return sailed wide.   

The Swiss broke Del Potro in the next game with a forehand volley winner at the net, after drawing the Argentinian forward with a delicate forehand drop shot, to lead 2-0.   

The next six games went with serve before Federer held in the ninth, clinching the opening set in 37 minutes when Del Potro dumped a forehand service return into the net.   

The Argentine was again broken in the first game of the second set, when Federer unleashed a crunching forehand crosscourt winner, and also in the fifth following another forehand winner by the Swiss.   

Oozing confidence, Federer served out to book his place in the last four, saving one break point in the eighth game before sealing victory on his third match point when Del Potro netted his service return.   

Federer, who had battled flu and a temperature to beat his first three opponents at Indian Wells, will face second-seeded Spaniard Rafa Nadal in Saturday's semi-finals.