World number one Roger Federer [ Images ] battled past Croatia's [ Images ] Ivan Ljubicic 6-3, 2-6, 7-6 on Tuesday to close in on the semi-finals at the season-ending Masters Cup.

The Swiss, who has just recovered from a six-week injury layoff, bounced back from a poor second set to make it two wins out of two at the troubled $4.45 million event in Shanghai.

Federer squandered three match points at 5-3 and 5-4 in the third before sealing victory 7-4 on a tiebreak to stay on course for a third straight Masters Cup title.

Only Ilie Nastase in 1971-73 and Ivan Lendl [ Images ] in 1985-87 have achieved three-in-a-row.

Federer was assured of finishing the second round of matches on top of the Red Group with Argentines Guillermo Coria and David Nalbandian [ Images ], who lost their openers, playing later on Tuesday.

The Masters Cup was hit by the sudden pullouts by former world number one Andre Agassi [ Images ] and French Open [ Images ] champion Rafael Nadal [ Images ] through injury on Monday.

The withdrawals were a further blow to organisers after the pre-tournament pullouts of Andy Roddick [ Images ], Marat Safin [ Images ] and Lleyton Hewitt [ Images ].