You might get the chance to sign him with a really good offer in the period where only you can negotiate with him before free agency. I had this happen with one SP who was going to go FA but accepted an offer of more than he was asking. But his message at the time was basically 'i'm going FA unless you overwhelm me". This might not apply to guy who gives the message "I'm going to see what FA has to offer. Let's talk in the off season". but it's worth a shot.