Del Potro through as Murray loses percentage game

Argentine defeats Federer to send both men into semi-finals at expense of Scot

Hopes of a home winner in the first end-of-season championships to be staged in Britain were dashed in the cruellest of fashions here last night.

Andy Murray was a clear favourite to go through to the semi-finals after beating Fernando Verdasco 6-4, 6-7, 7-6 in his final round-robin match in the afternoon, but, amid scenes of confusion and to the bewilderment of most in the 17,500 capacity crowd here, the world No 4 went out nearly six hours later when Juan Martin del Potro beat Roger Federer 6-2, 6-7, 6-3 in the last match of the day.

Murray, Del Potro and Federer had all won two of their three group matches, but it was the Argentine and the Swiss who went through thanks to their percentage of games won in the round-robin phase. Del Potro edged out Murray by virtue of winning just one more game than the 22-year-old Scot.

However, it was only several minutes after the end of the match that the outcome was confirmed, by which time many of the crowd had left. Even Murray, watching on television, was left bemused, posting a message on Twitter that read: "Anyone know what's going on? I think I'm out, but the rules aren't worded too well." Earlier in the day Murray had even asked an official during his match against Verdasco for clarification on the rules.

The tie-breakers in the round-robin format for this tournament have always been confusing at best and all but impenetrable at worst. Two players go through to the semi-finals from each of the four-man groups, but if two or more are level on wins a series of tie-breakers come into operation.

Murray would have been certain to qualify had he beaten Verdasco in straight sets, while any win for Federer over Del Potro would also have sent the Scot through. Had Del Potro won in straight sets – and he came within two points of doing so – the Argentine would have qualified alongside Murray.

As soon as the final match went to three sets, however, a win for Del Potro would mean that the Argentine, the Swiss and the Scot would all end on two wins and all with a record of 5-4 in sets over their three matches. In that case the two semi-finalists would be the two players with the best percentage record of games won over the whole round-robin phase.

With nearly everyone in the crowd oblivious to the mathematical implications, Federer had qualified for the semi-finals by the time he had won just one game in the final set. At 3-3 the Swiss needed to win only one more game – whatever the final score in the match – to send himself and Murray through. Federer had three break points in that game but failed to take any of them.

At 3-4, moreover, he played an atrocious game, a missed smash, a double fault and a ragged forehand helping Del Potro to break serve. The Argentine then served out for the match with his 11th ace. He had edged Murray out by the tiniest of margins, his win-loss record in games for the tournament standing at 45-43 compared with Murray's tally of 44-43.

Amid the confusion at the end of the match the del Potro's on-court interview was cut short. While officials sought guidance as to who had qualified, Del Potro resorted to a game of tennis with his friend, Carlos Tevez, the Manchester City striker, who had been watching in the crowd.

The tournament has been a huge success so far, with capacity crowds filling the arena for almost every session, but the end to this round-robin phase was a shambles. During the day Association of Tennis Professionals officials had twice changed their minds about the interpretation of its rules on tie-breakers and the lack of information for the crowd was inexcusable.

It was an ironic way for Murray to be eliminated given the circumstances in which Federer had gone out 12 months ago. In Shanghai last year Murray had already qualified for the semi-finals and did not need to win his last round-robin match, but knocked Federer out in a three-hour epic.

This time the outcome was tough on Murray, who was pushed all the way by Verdasco. Murray converted only one of his 13 break points in the match, on most of which Verdasco raised his game superbly. The Scot, meanwhile, saved the only break point that the Spaniard forced.

In the last match Del Potro served superbly. Just as he had in beating Federer in the US Open final two months ago, he regularly troubled the Swiss with his thunderous forehands.

By the end of the second set Federer had not forced one break point and at 5-5 in the tie-break was within two points of going out, only for Del Potro to miss an easy backhand and then set up a routine volley winner for the Wimbledon champion. The watching Murray might have wondered whether this was not going to be his day – and he would have been right.

ATP World Tour Finals: State of play

Group A

P/W/L/Sets/Games

R Federer 3/2/1/5-4/44-40

J M Del Potro 3/2/1/5-4/45-43

A Murray 3/2/1/5-4/44-43

F Verdasco 3/0/3/3-6/45-52

Group B

P/W/L/Sets/Games

R Soderling 2/2/0/4-0/25-15

N Davydenko 2/1/1/3-2/28-23

N Djokovic 2/1/1/2-3/23-28

R Nadal 2/0/2/0-4/15-25

The top two players in each group qualify for the semi-finals. If two or more players are tied on the same number of wins after the round-robin matches the following tie-breakers are used: 1 Winner of match between the players (if two are tied); 2 Player with highest percentage of sets won; 3 Player with highest percentage of games won.