Dennis has played mostly Futures and Challengers, reaching the quarter-, semi-, and finals of a number of events, but never winning a title. He qualified for the 2012 SAP Open in San Jose, California. He lost his first main-draw match to Bulgarian Dimitar Kutrovsky, another qualifier.
In the first match of the day, American Dennis Lajola lost his ATP Tour debut to fellow qualifier Dimitar Kutrovsky of Bulgaria, 6-7 (7), 6-3, 7-6 (3)
GO Roger Federer, Juan Martin Del Potro, Andy Murray, Thomaz Bellucci, Kei Nishikori, Jo-Wilfried Tsonga, Milos Raonic, John Isner, Alexandr Dolgopolov, Dennis Novikov and Bernard Tomic