Both defending champions of the Citi Open, Alexander Zverev and Ekaterina Makarova, will return to try and lift up titles at Rock Creek Park once again. The two join stellar fields on each side for the tournament's 50th anniversary. 

Looking Back At The Title Runs

Headed into the summer, Zverev was coming off of some big titles, capturing three titles and reaching four finals before coming to DC, including his first Masters title in Rome. It wasn't an easy road for the German, going the distance in his opening match against Australia's Jordan Thompson. He faced another tough battle against American Tennys Sandgren in the following round, winning 7-5, 7-5.

After that though, it was one-way traffic from the German, losing no more than four games in a set the rest of the way. He took out second-seeded Kei Nishikori in the semis before defeating 15th-seeded Kevin Anderson in the final. The German would follow his Citi Open title up the following week by claiming a second Masters title in Montreal, defeating Roger Federer to win the Coupe Rogers.

Makarova was having an exceptional summer. She claimed a massive upset victory over Australian Open champion Angelique Kerber in the opening round of the French Open and completed won the Ladies' Doubles title at Wimbledon with Elena Vesnina. She came in as the seven seed and took out American Jamie Loeb in the first round. She followed that up with a victory over 2016 Olympic Gold Medalist Monica Puig

In her quarterfinal match against Simona Halep, the Romanian would retire due to heat exhaustion in that match. The Russian was made to work in her last two matches, going the distance against both Oceane Dodin and Julia Goerges; she came down from a set behind in both matches. The win would give Makarova her third title in singles. 

Makarova with a kiss to her third career singles title (Icon Sportswire/Getty Images)
Makarova with a kiss to her third career singles title (Icon Sportswire/Getty Images)