if u havent seen him before how do u know how he is playing?
Folding, and going AI are out, but may be reasonable to raise here. Just because it is no longer the rebuy period doesnt mean he has you beat. Even more so if he is an expert - his raising range is wide, anywhere from KQ and up. Depending on how much more than 20 BB I have, since you just said more than, I may re-raise here about 2x...you will get most weaker hands to fold. If he then shoves you can fold unless you have a great read. Furthermore, if the flop comes all unders I would probably shove, obv unless I hit a set then Im check raising.
I would be more inclined to just call if I thought he was a maniac.