It was a very impressive win by the former world no.1 Roddick, who has been struggling with his form this year, dropping out of top 10.
Almagro desperately needed to win to boost his chances to qualify for the Barclays ATP Word Tour Finals in London. He is currently ranked 9th, only the first eight will qualify for the end year event.
Alexandr Dolgopolov of Ukraine also reached the quarterfinals, ousting Bernard Tomic of Australia 5-7, 6-1, 6-0.
Dolgopolov produced an amazing comeback. After losing the first set, he won 12 out of 13 games.