Great result. Dimitrov beat Nielsen 7-6 (7-5), 6-2 and Bulgaria won the mixed doubles 3-6, 6-4, 10-1.
Nielsen, who pushed eighth-ranked Mardy Fish of the U.S. to three sets on Monday, put up stiff resistance in the first set before Dimitrov dominated in the second.
"It was definitely a tough match today. The guy was attacking at every opportunity," Dimitrov said. "I got a bit lucky on some shots. He played some great tennis."