The Foro Italico has moved on from the more innocent days of 50 years ago, when a line judge turned round to buy an ice-cream from a passing vendor and missed a fault on a match point, to the era of the serial condom-thrower.

Yesterday's incident happened shortly before Roger Federer, the Swiss fifth seed, advanced to the final of the Rome Masters after Juan Carlos Ferrero retired due to inflammation of the right upper arm. The Spanish second seed will not play again before the French Open on 26 May.

"Be careful – use condoms!" a spectator shouted, hurling a packet or two on to the Centre Court. The police moved in and escorted the culprit out of the stadium, not for the first time here and elsewhere. On this occasion he was lucky to be noticed in the general pandemonium caused by one of the longest-delayed line calls one can remember.

Before the baseline judge gave his decision, ruling out a Federer shot when he had a break point while leading 6-2 3-2, the players had time for a mini-rally.

The British umpire, Mike Morrissey, checked the mark and confirmed the call, and Federer was so upset that he walked over and had a lengthy dispute with the umpire, arguing that the point ought to have been replayed. Ferrero joined the debate and then the condoms landed. When order was restored, Federer had another break point, which he converted for 4-2.

Federer won the first two points of the seventh game before Ferrero walked to the umpire's chair and said he was no longer fit to continue. "The problem began when I was playing in Valencia [last week]," he said. "It's nothing serious, but my arm is hurting. I've been travelling a lot and playing a lot of matches in a row. Maybe I need a rest."

The way Ferrero was making errors suggested that all was not well with him and, having been treated to some whistles of derision during the match, he was given a sympathetic cheer as he left the court.

Only Federer has won more matches than Ferrero this season – 35 to 33 – and yester-day's match was anticipated to be the showpiece of the tournament. It was their first meeting on clay, and both players have impressed on the sport's slowest surface.

Ferrero, who was runner-up to Albert Costa in last year's French Open final, arrived in Rome after winning the Monte Carlo Masters and his home tournament in Valencia. Federer, who won the Munich title last Sunday, had put together a run of 23 consecutive sets before conceding one to Filippo Volandri, an Italian wild card, in the quarter-finals.

Yesterday's match was an anti-climax, with only Federer on form, and even he seemed in danger of being dragged down to Ferrero's level at times because of the ease of the contest.

The first set was completed after only 27 minutes, Federer breaking serve in the fourth and eighth games. Ferrero managed to make a contribution in the first five games of the second set, after which he called for the trainer. All that remained was the mini-drama of the seventh game.

Federer, who won his first Masters Series title in Hamburg last year, will play Felix Mantilla, of Spain, who beat Russia's Yevgeny Kafelnikov 4-6 7-6 6-4 in the final. Kafelnikov served for the match at 6-5 in the second set.