It’s a stretch for the defense

San Antonio’s Tim Duncan is having a strong playoff series against the Lakers, averaging nearly 22 points and 18 rebounds over the first three games of the Western Conference finals.

But the Lakers have had some success defending Duncan with double-teams involving Pau Gasol and Lamar Odom.

By taking advantage of offensively challenged Fabricio Oberto or Kurt Thomas, the Lakers were able to gamble with this aggressive defensive tactic often in taking a 2-0 lead in the best-of-seven series.

In Game 3, however, San Antonio Coach Gregg Popovich turned to veteran Robert Horry at the power forward position and the results were positive.

Playing most of his playoff-high 18 minutes 21 seconds in the first half, Horry proved to be the right matchup against Odom because he provided a much-needed outside shooting threat for the Spurs.

That’s important for San Antonio, which relies heavily on spacing for its offense to work around Duncan.

Although Horry attempted only two shots and did not score in Game 3, his ability to shoot from the perimeter forced Odom to step outside on defense. This not only left Duncan alone against Gasol in the post but also opened driving lanes for Manu Ginobili and Tony Parker.

Horry got his first call with 6:37 remaining in the first quarter, shortly after Popovich had inserted Ginobili into the game. Lakers Coach Phil Jackson stuck with the same lineup, and that’s when the Spurs found their offensive rhythm.

Horry might have lost a step, but he played with fresh legs in Game 3 and his mobility around the perimeter helped trip up the Lakers’ defensive schemes.

Instead of getting a collection of defenders into the key with their hands ready to make plays, the Lakers found themselves standing around and spread out.

As a result, the Lakers’ team defensive rotations were a step slow and allowed Ginobili to find his scoring touch.

Horry was also a valuable help defender for the Spurs in Game 3.

Taking advantage of his knowledge of the Lakers’ triangle offense and Kobe Bryant’s offensive tendencies, Horry was able to effectively get into lanes while defending Odom at the same time.

For tonight’s Game 4, this is where the Lakers’ role players have to step up. Whenever the Spurs gamble defensively, the Lakers have to be willing to make the extra pass and have open shooters make shots.

That means perimeter players such as Derek Fisher, Vladimir Radmanovic, Sasha Vujacic and Jordan Farmar have to be ready to get the job done.

Summary: Popovich is not afraid to use a variety of lineups against the Lakers, and he did that in the fourth quarter of Game 3 to take advantage of Brent Barry, who was playing well off the bench.

Popovich removed Oberto and went with a small group that included Barry, Duncan, Ginobili, Parker and Bruce Bowen. Jackson countered with Luke Walton at power forward and put Odom on the bench. The Lakers did not threaten the rest of the game. Look for the Spurs to go with this look again in Game 4.

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lonnie.white@latimes.com