Watch: Rebecca Marino applauds Venus Williams in classy move after win at Citi Open

Rebecca Marino quickly halted Venus Williams' return to action as she mounted a comeback 4-6, 6-1, 6-4 victory over the seven-time Grand Slam champion at the Citi Open on Monday.

After her victory, Marino applauded Williams and directed the crowd to do so as well. The gracious act was uploaded on both the Tennis Channel and the WTA Twitter accounts.

An ace sealed Marino's three-set win over Williams. She pumped her fist in a subdued celebration, shook hands with Williams with a smile at the net and appeared headed towards her seat before turning to tap and wave her racket towards the crowd.

She then headed back to her bench but not without giving due respect to Williams. She stretched her arms towards the American, tapped her racket in the direction of her opponent and, as if that were not enough, pointed her finger at Williams to continue to urge the crowd to cheer for her. Placing her racket on her bag, the Canadian faced Williams and clapped her hands.

Twitter user @Tennis_Now noted Marino's class act, writing:

"Rebecca Marino doing the classy thing and clapping for Venus Williams after she edged out the American in three sets. Venus had a lead in the third but could not finish it off."

"Just a little rusty" - Venus Williams after her return from near one-year layoff

Venus Williams reaches for the ball in her match against Rebecca Marino at the Citi Open

Venus Williams returned to singles action after nearly a year, having last played in the Chicago Open last August. But the comeback did not end on a high note as she lost to Rebecca Marino despite taking the opener and holding a 4-1 lead in the final set.

Williams, who last played in the mixed doubles format with Jamie Murray at Wimbledon, attributed the loss to her lack of competitive action.

"Just a little rusty. I really put myself in good positions in the third set, too. Just trying to shake off some rust. That's just to be expected. All I can do is just play another tournament and play better," said Williams in an interview on the WTA website.

Williams started the match strong, grabbing the first set, 6-4, anchored on her reliable first serve. But she tumbled against the surging Marino who took the last five games of each of the second and third sets to prevail.

Williams served 13 double faults, four of which came in her last two service games. She will next play in Toronto and Cincinnati.