VIENNA, Oct 6, 2008 (AFP) - Former world number one Juan Carlos Ferrero upset fourth seeded Croat Ivo Karlovic 6-4, 7-6 (7/4) on Monday to advance to the second round of the Austrian Open.

Although Karlovic added a further 17 aces to the 848 he had already fired this season, the rest of his game could not match the standard shown by his Spanish opponent.

Ferrero also served so well that Karlovic failed to make many of his returns, he struck some fine groundstrokes, and hit several winners off of the intimidating Karlovic serve.

A break for 2-1 when Ferrero hit an impressive forehand winner down the line while on the run was enough to decide the opening set, although the Spaniard had to fight off a break point to hold for 4-2 and another as he served for the set.

After Karlovic survived two break points to hold for 1-0 in the second set games went with serve until the tiebreak, won with a mini-break on the first point.

Fifth seeded Spaniard Fernando Verdasco overcame Romanian qualifier Victor Crivoi 6-4, 6-4, and he will next play Guillermo Canas of Argentina, who earned a welcome 7-6 (7/2) 6-3 victory over Italy's Andreas Seppi.

Czech qualifier Jan Hernych edged past Roko Karanusic 4-6, 6-4, 7-6 (7/5) to set up a second round clash with top seed Stanislas Wawrinka, and there were also victories for Spaniards Carlos Moya and Feliciano Lopez.

Moya defeated Germany?s Michael Berrer 7-6 (7/5) 7-6 (8/6), and Lopez overcame Agustin Calleri of Argentina 7-6 (7/2) 7-6 (7/4).

Top seed Wawrinka, second seed Fernando Gonzalez of Chile and Argentine third seed Juan Martin Del Potro this week all have the chance to move into the eighth spot in the Race for the Tennis Masters Cup.

The top eight players will compete in the season-ending event in Shanghai, which takes place between November 9-16.

Less than 100 points separate current Race number eight James Blake and 22nd-placed Radek Stepanek. Blake surrendered his opportunity to solidify his position by withdrawing from Vienna for personal reasons.

Del Potro, runner-up in Tokyo on Sunday to Tomas Berdych, can overtake Blake by reaching the quarter-finals in Vienna, and move past number seven David Ferrer if he wins the title.

If Wawrinka, currently number 10 in the Race, wins the title he would move above Blake and Del Potro, if Del Potro fails to reach the final. A title for Gonzalez would move him up from 11 to eight in the Race.

'I need one or two more results and I?m working to earn this,' said Del Potro, who after being ranked 75 in April entered the world?s top 10 this week.

'I hope to continue this good form and qualify for Shanghai.'