A second round matchup at the National Bank Open between top ranked tennis pro Maria Sakkari and Danielle Collins erupted into a heated exchange Wednesday night when Collins took issue with Sakkari seemingly spiking a ball into the crowd. 

Collins, 29, took the first set 6-4 and was leading 2-1 in the second when the exchange happened. 

Danielle Collins plays the Canadian Open

Danielle Collins awaits a serve from Maria Sakkari of Greece in the second round on Day 3 of the National Bank Open Montréal at Stade IGA in Montreal on Wednesday. (Robert Prange/Getty Images)

Collins returned Sakkari’s serve, which had been called out, but the No. 8 ranked tennis pro then smacked the ball out of bounds into the crowd. She held out her hand as a gesture of apology, but Collins was already fired up over the act of unsportsmanlike behavior. 

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"Did you just see that?" Collins said to the chair umpire. "Did you see what happened?" 

Sakkari responded back that the ball "didn’t hit anyone," but Collins was not interested in any explanation. 

"Shut your mouth. Shut your mouth," Collins demanded.

Maria Sakkari plays the Canadian Open

Maria Sakkari stares at Danielle Collins during the second round on Day 3 of the National Bank Open Montréal at Stade IGA in Montreal on Wednesday. ( Robert Prange/Getty Images)

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The two continued to exchange words before the umpire signaled for both of them to move on. 

The match continued on and Collins advanced with a 6-4, 6-2 victory. She and Sakkari appeared to put the tense interaction behind them as they shook hands at center court afterwards.

Collins and Sakkari shake hands

Maria Sakkari, left, and Danielle Collins shake hands at the net after the second round on Day 3 of the National Bank Open Montréal at Stade IGA in Montreal on Wednesday. (Robert Prange/Getty Images)

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Collins will next play Canadian Leylah Fernandez, who also advanced to the round of 16 after beating 11th-seeded Beatriz Haddad Maia 7-5, 5-7, 6-3. 

The Associated Press contributed to this report.