It is a problem of traffic conditions not of long distances. You could get to the airport in 20 minutes from atocha at 9:00am on sunday
You can assume that AVE will be on time, one hour should be enough for transfering. But if it rains, traffic will be a variable you cannot control.
In case you are not carrying lots of luggage, subway is also an option, you can take it in the station itself and it is independent on traficc.
Nevertheless, I agree with the previous posting, situation is totally different if we are talking saturday or sunday, no problem then.