PSG meet Barca in the Champions League round 16 first-leg on Tuesday at the Nou Camp.
French reporter and Spanish football expert Frederic Hermel told RMC: "I have bad news for PSG. Messi is ready to receive PSG! A brace against Alaves? It's more than that. He had good games this season. There are signs that never fail.
"He was happy on the pitch, and when Messi is happy it hurts! He is released. He scores two sublime goals. When he's detained, he's fine. It's the smell of spring. Messi is good. (Antoine) Griezmann is still having a good game, even if he missed chances.
"Afterwards, Griezmann is not a boss, he's a secondary player at Barça, he's Messi's accompanist. He can be very good like that too. But PSG must be wary of Messi."