The Wizards just gave away a big in that trade. They weren't going to draft Allen. That's the kind of hindsight that isn't helpful. Yes, the Spurs could end up giving away a pick that's a really good player. They've done so in the past with guys like Dragic and Lee. That's not something to worry about. The Spurs made a win-now trade with DeRozan. They lost their chance at winning once Murray went down. But they still have one or two more years with their current core, and the goal is likely going to be to compete as much as possible with those guys signed. That means they'll need to clean up their roster and boost their rotation. The goal would be to get a guy into your team with a year to adjust so that when Murray comes back, the team is that much stronger.
I'm certainly am not talking about giving up an unprotected first for Avery Bradley or something. But the Toronto pick to turn Gasol into Carroll and Dinwiddie? Could make a really big difference next year when the team would be able to use their full MLE to attack their weaknesses rather than splitting it up again.