Why not

So many reasons why not.

Care to elaborate?
This should be good...

We don't need him. He doesn't fit in our system. He's getting slow. His skills are slipping fast. He'd take ice time away from Kyrou. Need any more?

Can help with additional goal scoring with Tarasenko gone, having a defensive system helps with his defensive flaws because everyone around him is good defensively, he’s actually not very slow at all, his skills are fine he got 34 points last year with an injury and playing on the 3rd and 4th lines while being harassed by the head coaches, Blues are in a possibly to repeat another cup and Kyrou is young and won’t produce as much as Kovi in the top 6. Kovalchuk was off to a good start this year. It wasn’t his fault. The Kings haven’t been fair to him one bit.

You have a funny idea of what constitutes a good start. And of how team defense works. Nah, I'll happily take Kyrou's production, which will eclispse Kovy's in no time. Dude, I watched him play KHL for SKA in person several times - he was slow for that league two years ago. Huge no thanks.