It cannot be said the Spurs spent their three weeks sans All-Star point guard Tony Parker simply sitting on their hands. With a wet-behind-the-ears 21-year-old replacing their leading scorer, assist man and overall offensive engine, the Spurs still went 6-2 and extended their lead over Oklahoma City in the Western Conference race to 2???1/2? games. Now that Cory Joseph has handed the keys to the car back to Parker, here comes the hard part for the Spurs. “Just because a player is healthy, that’s just the first step,” coach Gregg Popovich said. “It takes time, not just for that person to get his rhythm back and feel confident, but other players have to get used to the new player also. People always forget about that.” Over the final 13 games of the schedule, which resumes Sunday night in Houston, the Spurs aim to rediscover the groove they were in March 1, when Parker sprained his left ankle in a win over Sacramento. True, remembering how to play with an All-NBA point guard in the lineup would likely be high on any team’s mythical list of “most desirable problems to have.” As Friday’s rough-around-the-edges 104-97 overtime victory over Utah can attest, the re-learning process can take some time.