Carlos Alcaraz revealed which player he deemed “unplayable” during a practice session on Sunday, ahead of the Vienna Open.

On Tuesday, the world No. 3 dispatched Karen Khachanov 6-4, 7-6(5) to set up a second-round clash with either home favourite Jurij Rodionov or last week’s Almaty finalist Nikoloz Basilashvili.

Despite going a break down early in the first set, Alcaraz produced some of his best tennis to edge past Khachanov – a performance the Spaniard would have preferred to his practice session against world no.22 Andrey Rublev on Sunday.

Carlos Alcaraz: Rublev was ‘unplayable’ in practice

Alcaraz was asked about a practice session with Rublev that saw the Russian earn a comprehensive 6-2 win over the world No.3.

The Spaniard, a seven time Grand Slam winner, said that while he was “playing good”, his opponent was “unplayable”.

“Of course. Sometimes it's really difficult to see the reality of the things, you know. When I was practicing with Rublev, I lost 6-2, but I was playing good," Alcaraz said.

"He was unplayable, ripping every forehand, hitting the ball really hard with the backhand. I couldn't be aggressive at all, not even one or two shots.

“That's why I left the court a little bit unhappy, but at the same time thinking, all right, I'm doing the right things."

However, Alcaraz said he tried to focus on the positives in his own performance rather than the score line.

Alcatraz added: “You know, sometimes in tennis you're playing against someone and they try not to let you play sometimes, but in those days I just left the court thinking about what I've done great.

“I think that day I did a lot of good things, to be honest. I learned a lot from those days as well.”

Carlos Alcaraz addresses return from injury

Alcaraz’s season came to an abrupt halt in April when a wrist injury forced him to withdraw from the Barcelona Open.

He did not return to competitive action until the US Open in late August, where he was knocked out by Ben Shelton in a five-set quarter-final thriller.

His form since then has been mixed, with a title triumph in Tokyo followed by a surprise defeat to Zizou Bergs in Shanghai.

On his return to fitness, Alcaraz said: “Well, I'm in the right way. I think I'm doing the right steps. So I'm just happy with everything I've been doing lately. We could see today, I think today I just played a great tennis.

"What I really wanted to get is about the consistency that I got at the beginning of the year, of playing such a great tennis or finding the solutions during every match.

"That's the level, that's the thing that I want to get back and I think I'm doing the right steps. Where am I from that? I'm not sure I can answer that, but I'm on my way."