No.8 seeds Katerina Siniakova and Taylor Townsend are at the top of the Green Group table after Monday's round-robin doubles matches at the WTA Finals Riyadh presented by PIF.

WTA Finals Riyadh: Scores | Schedule | Standings

Siniakova and Townsend took a 2-0 lead in the group with a 6-2, 6-2 defeat of No.6 seeds Nicole Melichar-Martinez and Ellen Perez in just 68 minutes.

Later, reigning Australian Open champions Hsieh Su-wei and Elise Mertens needed to win their match to stay alive. No.3 seeds Hsieh and Mertens did prevail over No.1 seeds and reigning US Open champions Lyudmyla Kichenok and Jelena Ostapenko 6-1, 6-3 in 67 minutes.

Here are Green Group scenarios:

  • Hsieh and Mertens will advance as group winners with a victory Wednesday. Siniakova and Townsend will finish second, regardless of their result.
  • Siniakova and Townsend will advance as group winner with a victory Wednesday. Melichar-Martinez and Perez will finish second with a victory, otherwise Hsieh and Mertens will finish second.
Green Group 3x2

Siniakova, Townsend stay undefeated: Monday's first contest pitted the winners of Saturday's opening round-robin matches against each other. It was Wimbledon champions Siniakova and Townsend who will go into Wednesday's final day of group action at the top of the standings, after they beat Melichar-Martinez and Perez.

Though each player on court had faced her individual opponents multiple times before, this was a first-time encounter between the two teams that promised to bring a new dynamic to the rivalries.

In the event, Siniakova and Townsend -- who are playing only their eighth tournament together -- executed an ultra-aggressive strategy that enabled them to dominate throughout.

Must See

"I thought we came out very clear with our game plan," said Townsend afterwards. "The first match [in which they saved match point to defeat Lyudmyla Kichenok and Jelena Ostapenko] really helped us shake out the nerves. We trusted in ourselves and it shows."

Siniakova agreed. "We wanted to be aggressive, we wanted to get those volleys," she added.

Townsend's leaping backhand volleys proved key, and the American pulled a series of the crowd-pleasing shots off when closing out both sets. The 28-year-old was only the only player on court who didn't drop serve, saving both of the break points she faced in the second set.

Siniakova also showed off her prowess at net, as well as the extra gear of creativity that has helped her win nine Grand Slam doubles crowns with a remarkable forehand slice winner early in the second set. The pair found 16 winners overall against just 12 unforced errors.

Melichar-Martinez and Perez were afflicted by ill-timed double faults. Perez committed the first to drop serve in the opening game, and from that point on the American-Australian duo were chasing in vain for the rest of the match.

'This is pure skills': Hsieh's best net plays in WTA Finals must-win match

Hsieh, Mertens extend hopes: Hsieh and Mertens had to win the late-night tilt to stay alive once Siniakova and Townsend won the earlier match.

The combination of Mertens' powerful returns and Hsieh's deft volleys was potent, and they quickly jumped out to a 5-0 lead on Monday. They took the first set 6-1 -- but they also won their first set 6-1 on Saturday, and still lost that match to Melichar-Martinez and Perez.

In fact, Hsieh and Mertens did fall behind an early break in the second set again on Monday, but the pairing rebounded and they broke Kichenok for a 5-3 lead. Serving for the victory, a Mertens ace queued up match point, which they converted after a long Kichenok return.

Hsieh and Mertens were clutch in pivotal moments during the clash between this year's hard-court Grand Slam champions -- they won five of the seven deciding points in the no-ad encounter. Overall, they converted six of 15 break points to keep their semifinal hopes active.