He is not a good target. And given that it would take a ridiculous offer to pry him loose -- seeing as how the Trail Blazers have pretended he's a star in the making since they drafted him -- he is not worth it. He's a decent and still intriguing player, but he's not nearly the defender he's reported to be and is merely an ancillary scorer.
Leonard has a higher upside and Green has shown himself to be a decent backup. The Spurs shouldn't waste a cent on the small forward position, unless they end up trading Anderson and need a depth guy (I'm presuming Jefferson will be amnestied, of course). Even that, they may have somewhat in house, depending on how Butler progresses with the Toros.