Defending champion Elina Svitolina is through to the semi-finals of the WTA Finals in Shenzhen after an accomplished victory over Simona Halep.

The Ukrainian, who now has back-to-back wins over top five ranked opponents, showed greater consistency than her Romanian opponent to secure the match 7-5 6-3. 

The result means she qualifies for the semi-finals as Purple Group winner.

Svitolina broke in the very first game thanks to a flurry of errors from Halep, but when the Romanian found her aggression and consistency back, she levelled by breaking to love.

Both players saved break points on their own serve late in the first set, but in the 12th game Svitolina’s constant attack drew errors from Halep and allowed her to take the first set.

It seemed as if an intervention from coach Darren Cahill, just like in her first match against Andreescu, was going to pay off for Halep as she broke early in the second set with a clean backhand return.  

However, Svitolina showed resilience as she broke straight back and in the process hit possibly the shot of the year with an outrageous short spinning forehand which Halep had no answer to. 

It seemed to dishearten Halep, whose number of unforced errors reached 38, as Svitolina closed out another brilliant victory.

The defending champion has not lost in her last eight matches at the WTA Finals, having gone unbeaten in her title victory last year, and winning her final group match of the 2017 edition.

Meanwhile, Andreescu, who lost narrowly to Halep in her first match, was forced to end her clash with Pliskova prematurely because of an injury to her left knee, meaning she will play no more part in the tournament.

The Canadian broke in the opening game, but called for a medical timeout as soon as she consolidated the break.

Her left knee was taped up and this was when her Czech opponent took full advantage.

Pliskova broke twice to take the first set 6-3, which ultimately resulted in Andreescu walking to the net and retiring.

Pliskova and Halep will play each other on Friday, with the winner sealing the final qualification place from the Purple Group.