WTA Finals: Agnieszka Radwanska bt. Simona Halep

Radwanska blazes through the second set to take it 6-1. With this victory, she ensures Sharapova's semis berth as her own participation hinges on Pennetta's performance against the Russian.

Unreal Set Point! @ARadwanska wins the opening set vs Halep 7-6(5)! #WTAFinals https://t.co/3eI3qP6YIW
— WTA (@WTA) October 29, 2015

Radwanska's first set win means that Maria Sharapova is now automatically through to the semifinals at the Open.

Radwanska closes out the first set tie-breaker to take it 7-6.

Tie-break! #WTAFinals https://t.co/uKuevYZlfu
— WTA (@WTA) October 29, 2015

The first set goes into a tie-break with the scores level at 6 games apiece.

Radwanska holds serve to take a 6-5 lead against Halep.

Halep holds, with Radwanska unable to break and missing out on the set. 5-5.

It's set point now as Radwanska looks to close out the first set 6-4.

Game point! Could Radwanska turn the tables to take the lead from Halep?

Radwanska won't back down! The pair are now up 4-4 in the first set.

Only way Radwanska can make #WTAFinals SFs is... Defeat Halep in 2 sets & Sharapova defeat Pennetta in 2 sets!
— WTA (@WTA) October 29, 2015

Radwanska takes the lead 4-3.

Radwanska equalises! She equals Halep 3-3 in the first set, and necessarily needs a straight-sets victory here to progress in the tournament.

Halep can make #WTAFinals SFs if... Win in 2 sets Win in 3 sets & Pennetta not defeat Sharapova in 2 sets Lose in 3 sets & Sharapova wins
— WTA (@WTA) October 29, 2015

And a mere 8 minutes into the match, Halep is 2 games up against Radwanska, fresh off two losses.

Halep quickly closes out the first game!

The Polish ace and 5th seed in Singapore lost her first match to Maria Sharapova in a three-setter, then suffered a straight sets loss to Flavia Pennetta.

Radwanska comes into today's match having not won a single match at the tournament so far.

She beat US Open winner Flavia Pennetta in straight sets in her first match of the tournament, but faltered against the Russian former World No. 1

Top seeded at the tournament, World No. 2 Simona Halep comes into today's match fresh off a straight sets loss to Maria Sharapova.