ST. POLTEN, Austria, May 22 UPI) -- For the second time in 13 days, Chile's Marcelo Rios came out on top against Argentina's Mariano Zabaleta Saturday in the final of a claycourt tennis tournament, but this time Rios received a little help from an injured knee. Rios, the second seed, defended his title and won here for the third time when Zabaleta was forced to retire just 28 minutes into the final of the International Raiffeisen Grand Prix. In one of the year's most entertaining matches, Rios scored a 6-7 (5- 7), 7-5, 5-7, 7-6 (7-5), 6-2 victory over Zabaleta to win the German Open on May 9. Saturday, he earned his second title of the year, 14th of his career, and $57,000. With the score tied at 4-4 and Rios leading 30-0, the fifth-seeded Zabaleta aggrivated the left knee injury he suffered in Friday's semifinal victory over world No. 1 Yevgeny Kafelnikov of Russia. Rios, a former No. 1, has gotten his game back in top form and improved his 1999 record on clay to 20-4. One of those losses was a first-round defeat to David Prinosil in last week's Italian Open. But before the German Open, he reached the final of the Monte Carlo Open, retiring in the second set against Gustavo Kuerten. These results have left Rios optimistic of his chances at the French Open, which begins Monday. ``I'm in good shape, playing well, and am going to play better than last year,'' said Rios, a quarterfinalist last year. He opens this year's event against a qualifier. Zabaleta, 21, had been playing the best tennis of his career. In addition to reaching the finals of the German Open, he reached the BMW Open semifinals the week before and lost to countryman Franco Squillari. His first-round opponent at the French Open is also a qualifier.  