Barty went down 7-5 7-5 after a clinical victory from Halep. It was her first loss to a top-five player this year.

"For me, it's a huge victory," Halep told press after her win.

"It's a huge match that I played today. It means a lot that I could win this match.

"It was very difficult and every point was important.

"I tried to stay calm during the points because sometimes I force and I miss, but with [Barty] you have to keep the ball on court and try to mix also like she does."

Barty, who is world No.9, headed into the match recording the hottest start to a tennis season by an Australian in 16 years.

However, in her first clay quarterfinal, Barty wasn't able to overcome the reigning French Open champion. 

Halep, who won the title in Madrid in 2016 and 2017, put 87 per cent of first serves into play and had a 75 per cent success rate of winning points.

While Barty had 22 winners, the 23-year-old was undone by her 37 unforced errors.

The Australian never gave up when she was broken and fought to keep herself in the game, breaking back twice to level the sets.

One of the top moments from the game was a drop shot from Barty when she was 2-0 down in the second set.

Despite the loss, Barty is expected to rise to at least No.8 when the world rankings are updated this week.

Barty now turns her focus to Rome for the Internazionali BNL d'Italia which begins on Monday (CET).