How long should I wait to use a power trained player after power train?

[Tactician]

Just bought a fast trainer and trained him close to 7 stars, how long do you guys think I should put him on bench before include him in starting line up?

I am crazy about this season, a disaster to me, so have to buy this fast trainer and power train him. But I don't want to rush to use him as I heard about some past experiences that it would be better to wait for a couple of days.

I have noticed that some players bought from the transfer market, despite being rated 5 stars and at least decent trainers, they fail to impress during the first matches in any of the competitions, unless you are playing against a bot or against an abandoned team that has already declined. But, this may be different for a 5 star player trained to 7 stars.