The Doctor did it again. Croat Ivo Karlovic upset fourth-seeded Tomas Berdych (above) 7-6 (7), 7-6 (4) at the Qatar Open in Doha Monday night in a first-round shocker. Actually, for Doctor Ivo, it wasn’t all that shocking. It was the second time in two months that the 6-foot-11 Karlovic has defeated the No. 7-ranked Czech. Karlovic edged Berdych 4-6, 7-6 (4), 7-6 (2) in the first round at Basel in October. The two matches were eerily similar. Berdych never lost his serve in either match, and faced only one break point, that being in tonight’s encounter. But as he so often does, especially in tiebreakers, Karlovic, ranked No. 78, wins the biggest points. The Croat saved a set point at 5-6 in the first-set tiebreaker with a strong serve and volley, and got the crucial mini-break with a crushing forehand return of serve to go up 8-7. Karlovic served an ace to close out the set. The second set tie-break swung on another forehand service-return winner, this one to give the Croat a 5-4 advantage. Karlovic blasted two aces and the match was over in one hour and 47 minutes. “I was really focused,” Karlovic said. “I was just trying to hold serve as much as I could so that hopefully he would make a couple of mistakes in the tie-breaks — and he did.” Karlovic served 25 aces, saved both break points against his serve, and had 49 winners, while Berdych had eight aces and 28 winners. Berdych had just 10 unforced errors, while Karlovic committed 24. “I have played four tie-break sets in a row with him now, and it’s hard to play against someone who serves that well,” Berdych said. “It’s also difficult to find my rhythm. Ivo is not an opponent you appreciate playing early on.” Karlovic improved to 4-2 against Berdych.