Rafael Nadal made an unconvincing start to his 2016 season as he fought back to beat Pablo Carreno-Busta at the Qatar Open, but defending champion David Ferrer was a shock first-round casualty.

For the first time since 2004 Nadal failed to win a grand slam title last season, but the Spaniard finished 2015 well leading to hopes of improvement this time around.

The world number five made a slow start in Doha, though, before his quality eventually shone through in a 6-7 (5-7) 6-3 6-1 victory.

Carreno-Busta went toe-to-toe with Nadal to clinch the opener, but he had little reply when the 14-time slam champion upped the tempo in the second set.

Nadal broke at the first time of asking in the decider and, although he handed that straight back, he reeled off five straight games to reach round two.

However, compatriot Ferrer - who beat Tomas Berdych in last season's final - was out of sorts as he fell to a 6-7 (8-10) 6-3 6-2 defeat to Illya Marchenko.

It marks the first time that Marchenko, ranked 94th, has beaten a top-10 player and fourth seed Ferrer - who won 19 out of his first 20 matches in 2015 - admitted his opponent deserved to progress.

"He was better than me all the match," Ferrer said after the defeat. "From the first set, he deserved win the match. I didn't obviously play my game."

Third seed Berdych safely came through the first round with a 7-5 6-4 beating of Sergiy Stakhovsky.

Leonardo Mayer thrashed Benjamin Becker 6-1 6-2, but sixth seed Andreas Seppi was left reeling by a brilliant Ricardas Berankis display - the Lithuanian triumphing 3-6 6-1 6-4.

Pablo Andujar was taken the distance in a 6-4 0-6 6-4 victory over Paolo Lorenzi, while Teymuraz Gabashvili and Paul-Henri Mathieu also needed three sets in their victories over Simone Bolelli and Albert Ramos.