If he was having any symptoms then they would be identified in the extensive range of health checks they do with players. They all use apps to record health markers each day now on a range of things, as well as the other regular screens that happen.
If they was the hint of a problem then he wouldn't be playing footy.
I don't know what he thinks about, hence the use of the term 'guess'. My guess is based on the fact he came out and said people shouldn't blame Dangerfield for the clash, it was an accident and just a normal footy contest, so I think it is unlikely he is too bothered about it now.