I haven't been able to track down the original source of the following quote, but it is entirely consistent with Karpov's approach to the game:
In a recent interview with Big Think, Karpov explains his style.
"Let us say the game may be continued in two ways: one of them is a beautiful tactical blow that gives rise to variations that don't yield to precise calculation; the other is clear positional pressure that leads to an endgame with microscopic chances of victory [...] I would choose the latter without thinking twice. If the opponent offers keen play I don't object; but in such cases I get less satisfaction, even if I win, than from a game conducted according to all the rules of strategy with its ruthless logic."
One of the best performances of Karpov's career was at the 1994 Linares chess tournament where he crushed an outstanding field of the world's best grandmasters, including Kasparov, Shirov, Kramnik, Kamsky, Anand, Topalov and Polgár (Judit). There he played one of the best games of his career, against Topalov. Some chess enthusiasts call it Karpov's Immortal.