[Rabz]

No we shouldn't be worried.
He might be lazy, but still holds the No 1 ranking in the world.

This things are different to individuals.
Some trains really hard yet can't deliver to their potential, and there are some really talented individual who does just the bare minimum but still produces amazing results.
I'm sure Shakib knows how much he needs to do to perform at his best level.

Also sometimes, this things depends on how much he is being challenged in the team.
He IS Shakib Al Hasan, so his worth with the Bangladesh team is beyond any doubt.
The moment he realises that he is not competing with rest of the team mates, but with the rest of the best this world has to offer, it will bring a new challenge for which he will need to pick up the paces and Inshallah he will.

Your input will only reflect your desired level of output.
Now that the bar has been raised ( and hopefully he realises that), his input will also change.