Stupied call?

[kingstalker]

Pokerstars 20+2 one table
blinds 100/200 with 25 ante
I have 9000 in chips
My opponet 4260
I have [img]/images/graemlins/spade.gif[/img]J [img]/images/graemlins/spade.gif[/img]6 in the small blind
I complete, my opponet checks
Flop is 7-6-A, I bet 600, my opponet calls
Turn is A I check, my opponet checks
River is a 6 My opponet goes all in for 2000, I call doubleing him up,now I figured there was a good chance he had a ace but also I had a lot of chips so I could afford to take a hit, but still was my call stupied? It was only later did I realize this guy slow played every single decent hand he had and I finally stop betting his hand for him but it was too late at that point.