Hi we land in Madrid at 9am. Do you think we can make the 11am train to Seville?
Carolyn,
That's questionable. There may be unforeseen delays ( flight, passport control, baggage claim, etc,etc.) and therefore it's not advisable to book your train tickets for day of arrival in advance.
If you absolutely must book your tickets in advance, then I think it's wise to give yourself a large time cushion of at least 3-4 hours.
Are you going to Granada? Don't forget to book your Alhambra tickets way in advance!
Even if the stars aligned perfectly I think around midday would be the earliest possible you could hope for. Still, I would want to build in 4-5 hours safety time, just in case. You can always store your bags at Atocha, have lunch, stroll el Retiro.
Go for it but don't buy the tickets until you get there.