The Vikings took a gamble by playing tender-kneed QB Tarvaris Jackson against Kansas City in Friday's exhibition game. There is little doubt that the Vikings are shopping Jackson but if he were to get hurt in the preseason, they would be liable for his $600,000 salary until he recovers. Jackson, 26, had a near-perfect outing against the Chiefs, and that could improve the draft pick, to maybe a fourth-rounder, the Vikings might get for him in a trade.