Andre Agassi withdrew from the SAP Open with a lower back strain in his latest setback by an injury. Agassi, the second seed in the event which begins Monday, told tournament director Bill Rapp on Sunday night that he couldn't play. Agassi experienced severe pain in his lower back and down his legs during a workout Sunday, tournament officials said in a news release. Agassi, 35, has played only four matches since reaching the U.S. Open final last September. He sprained his left ankle playing racquetball Oct. 12 and aggravated the injury during the season-ending Tennis Masters Cup in Shanghai, where he was upset by Nicolay Davydenko in the first round. He pulled out of last month's Australian Open because of the injury and then lost to Guillermo Garcia-Lopez in the quarterfinals of the International Tennis Championships earlier this month in his first tournament of the year. Agassi is currently ranked eighth in the world by the ATP. His only tournament win last season came in Los Angeles and he lost to world No. 1 Roger Federer in the U.S. Open final in September.