if Sampras had lost numerous times to Krajicek in slams you would have a point but it was only once. One loss isnt anything concrete to form any valid argument upon. Lord knows even Federer has had his share of embarassing losses in slams, losing twice to Berdych in slams now, a player everyone knows is not and never will be slam caliber (atleast Krajicek won the one he beat Sampras in, something Berdych will likely never do), losing to a hip crippled Kuerten who was about 20% his old self at the 2004 French and this one was definitely in the midst of his "prime", losing to headcase Tsonga from 2 sets up at Wimbledon. If he plays until he is no longer in the top 10 as Sampras did he will probably have his own "Bastl" moment at some point too. He nearly did at Wimbledon 2 years in fact with Falla.
Hey, it's better to lose the a player the caliber of Berdych once or twice in the later rounds than to lose to the likes of Yzaga, Ramon Delgado, Gilbert Schaller, Karol Kucera. But, I guess losing to Berdych in the QF of the US Open and Tsonga in the QF of Wimby is unforgivable? LOL, where do you come up with this stuff? Yeah, he almost lost to Falla and Janko Tipsarevic, and Julien Benneteau. But guess what, almost only counts in horse shoes and hand grenades. Hell, when was the last time Federer lost to someone that wasn't a slam champion or a finalist in a slam? My guess is you'd have to go back quite a ways.