With Dirk Nowitzki sidelined because of a sore right knee, the Dallas Mavericks discovered how difficult it is to win without their star player.FC Barcelona Regal had five players in double figures and beat the Mavericks 99-85 in a preseason game Tuesday in Barcelona, Spain. The loss sent the Mavs home with a 1-1 record as they earned a split of this weeklong European trip, which included Saturday's 89-84 victory over Alba Berlin.The Mavs' next preseason game is at 7:30 p.m. Monday at American Airlines Center against the Houston Rockets.With Nowitzki, the Mavericks turned the ball over 27 times against Alba Berlin. Without Nowitzki against FC Barcelona Regal, the Mavericks were simply outmanned by the 17-time Spanish champions."Barca is a great team," coach Rick Carlisle said. "I admire the way they pass, move the ball, cut and make screens."Nowitzki started experiencing soreness in his right knee during Monday's practice. While the Mavs said the injury isn't anything serious, they weren't going to take a chance."Last year I dealt with [knee swelling]," Nowitzki said. "We did treatment twice and the swelling didn't come back. Hopefully it will respond next week and I can play through the year. It's unfortunate -- I would have loved to play -- but the preseason is not the time to force a swollen knee."In the game itself, after an early seven-point lead, Dallas trailed 21-19 at the end of the first quarter, 42-40 at halftime and 74-56 going into the fourth period.Chris Kaman led the Mavs with 15 points and 10 rebounds, Darren Collison had 14 points and four assists, and Elton Brand, who started in place of Nowitzki, finished with 10 points.Cuban's comebackOne day after Brooklyn Nets point guard Deron Williams said owner Mark Cuban's absence from a July meeting helped pave the way for him to sign a free-agent contract with the Nets, Cuban responded."I'm a big D-Will fan, but I'm kind of surprised that he would throw his front office under the bus like that by saying that I would make a difference," Cuban told reporters Tuesday in Barcelona. "I'm flattered that he thought my presence would have made more of a difference than what the Nets' management did."