Has Tim Duncan become a defensive liability?

When you consider that in the closing minutes of Game 2, the Suns repeatedly chose to attack Duncan with Steve Nash and Amare Stoudemire in a pick-and-roll situation, it's a fair question to ask.

The Nash-Stoudemire high screen action is one of the most lethal weapons in basketball, but the frequency with which Phoenix deployed it against Duncan was disarming for anyone who's watched the future Hall of Famer play defense since his days at Wake Forest. In his prime, few big men multitasked pick-and-roll defense the way Duncan could. He had the intuition, reaction and agility to harass the craftiest ball-handlers, while simultaneously checking the screener. Duncan almost always seemed to guess right -- but it wasn't guesswork at all. Duncan's instincts guided his movement on the defensive end of the floor.

Wednesday night in Game 2, Duncan seemed ill-equipped to deal with the speed and precision of Nash and Stoudemire, and the Suns made the Spurs pay for that vulnerability. Time catches up with every athlete -- ask anyone who watched Willie Mays stumble around in centerfield in Shea Stadium during his twilight years. Duncan certainly isn't that desperate. Even at his most exposed, he's no worse than average for an NBA big man on the pick-and-roll. Still, his Game 2 performance clearly suggests that Duncan is no longer an asset in this capacity, at least not in the Spurs' current defensive scheme.

Is this assessment too harsh? I took the question to David Thorpe: