Someone already posted the Doc Rivers interview here, so I won't repost, but David has repeatedly recounted stories about how he couldn't guard Timmy during that 1997 training camp.
Again, Robinson is a top 20 all time player, and one of the most athletic players in the history of the game who also possessed a great faceup game. HOWEVER, Timmy was no slouch athletically, was more coordinated than David, more skilled, had just as good of a faceup game (if not better), and a much better post game.
These comments are no knock on David, a guy who helped create the foundation for the Spurs as a model franchise, but Timmy was just that good in his prime. Again, we won championships with a high post iso as our go-to play.
And for all of those knocking David's teammates and going on and on about how much help Timmy had. Please look at our rosters from 2002-2004.
Starting 5 2002:
Parker (rookie)
Steve Smith (about to retire)
Bruce Bowen
Timmy
DRob (injured for a good portion of the playoffs and was essentially useless against the Lakers in the semifinals)
2003:
Parker (still inconsistent, nowhere near where he would be later)
Jackson (our 2nd best player, cut by the Nets the year before)
Bowen
Timmy
DRob (still a defensive anchor, but a s of his former self due to injuries/father time)
2004:
Parker (started to find himself in this season, but still couldn't shoot to save his life)
Ginobili (started to find himself as well, but still erratic and wouldn't erupt until a year later)
Bowen
Timmy
Nesterovich (average, run-of-the-mill center...and that's being nice)
In those 3 seasons the Spurs were ranked no lower than 3rd in the West, won one championship, and came damn close in 04. That 2002 team also went toe to toe with the 3-peat Lakers, but couldn't hold a lead in the 4th quarter to save their lives.