The deal has numerous incentive clauses, particularly in the option years, that will help protect the Rays if Shields doesn't live up to expectations or reward the pitcher if he continues on an upward trajectory. If all the options are picked up, Shields would give up his first two years of free-agent eligibility to remain in Tampa Bay.
Smart move, as was the Carlos Pena deal from last week.
Now: I don't follow the Rays all that closely, but what's going on with Scott Kazmir? I know he got a one year deal to avoid arbitration, but given that he is younger, better, and closer to free agency than Shields is, why aren't the Rays trying to lock him up too?