“You’re working as hard as ever, but now, ‘hard as ever’ isn’t enough.”

Coach Pepe Vendrell had those words to say to Roberto Bautista Agut following the Doha champion’s 6-7(6), 6-3, 6-2, 4-6, 6-4 win over sixth seed Marin Cilic in the fourth round of the Australian Open. The victory over last year’s runner-up marked a breakthrough for Bautista Agut: In his 10th fourth-round appearance at a Grand Slam, the 30-year-old finally reached his first quarter-final.

Back to work on Court 16 at Melbourne Park to prepare for his inaugural quarter-final match, coach and player are devising a plan to build on what’s already been the ideal start to 2019. The 22nd seed Bautista Agut is tied with #NextGenATP Aussie Alex de Minaur for most tour-level wins this year (9), and he claimed his ninth ATP Tour title by lifting the Qatar ExxonMobil Open trophy to begin the campaign.

So what’s the secret to his boost in form?

“The maximum effort has always been there,” Vendrell said. “But I think we’re maturing as a team, in terms of processing information and understanding what’s happened and why it happened, as opposed to focusing on just whether Roberto won or lost. I’m analysing things from a different perspective now. We won a tournament, but how did we go about doing that? We’re into the quarter-finals [at the Australian Open], but what did we do differently to achieve this?”

Bautista Agut agrees.

“These days, I’m able to single out the small differences I made during my matches. I can look back and see a subtle change in the way I handled a certain moment and how it differs to ways I reacted to those types of situations in the past,” Bautista Agut said. “I’m more level-headed as well. I focus more on myself and less on my opponents. In that regard, I feel more confident when I step on the court.”

Already this year, Bautista Agut has wins over Novak Djokovic, Andy Murray, Tomas Berdych, Stan Wawrinka and Cilic, the latest coming after three hours and 58 minutes in Melbourne on Sunday. The victory means the Spaniard has met a goal he set for himself in the preseason: to break through that fourth-round barrier at a Grand Slam.

“One of my goals before the start of 2019 was to reach the quarter-finals of a major,” Bautista Agut said. “Marin made that very difficult, but I think I played at a very high level against a top-level player. I’ve been in-form here and I feel especially good playing on these courts and under the current conditions.”

After 14 hours and 18 sets in four matches, Bautista Agut has been dubbed “Marathon Man” and for good reason: Before defeating Cilic, the Spaniard also needed five sets to overcome Andy Murray (6-4, 6-4, 6-7(5), 6-7(4), 6-2) and John Millman (6-3, 6-1, 3-6, 6-7(6), 6-4) in the opening two rounds in Melbourne, before defeating 10th seed Karen Khachanov in straight sets. Despite all that time on court, the World No. 24 feels he isn’t any worse for the wear and he is eager for more success.

“I was forced to battle my way past Cilic, but I’ve been fighting throughout the tournament,” Bautista Agut said. “But I’m not tired. I’m holding up well physically and I’m used to recovering quickly after these types of matches.”

The excellent level of play and bounds of confidence are there, and the results have been stellar so far. After working hard with his charge throughout the pre-season, Vendrell isn’t surprised with Bautista Agut’s recent surge.

“He’s talented, committed and a hard worker, and he’s working especially hard every day to raise his game,” Vendrell said. “So it doesn’t surprise me when I see Roberto earning victories like these, and I say that with humility and all due respect for his opponents. But it’s no coincidence Roberto is stringing together wins like he has been. We’ve stressed recently the importance of focusing on what we have to do in critical situations and not on what the opponent might do. We can’t control that, but we can control how to handle those big moments.”

Fast starts to the year are nothing new to Bautista Agut. He kicked off 2016 by lifting the trophy in Auckland. In 2017, he captured the title in Chennai. In 2018 he again conquered Auckland and this year he emerged victorious in Doha. But this season is proving more special than years past, for both player and coach.

“With all the victories I’ve had so far, I consider this to be the best January of my career,” Bautista Agut said.

“It’s not by accident when you accomplish something like that four years in a row,” Vendrell added. “It suggests that this time of the year suits us. I’m in tune with Roberto and I’m aware these types of conditions suit his style of play. We’re starting the season well-rested but also having laid the groundwork by planning and preparing in practice. I think we found the ideal approach to start a season.”

With nothing to prove and even less to lose, Bautista Agut will step on Rod Laver Arena for the first time in this year’s Australian Open campaign with another tough task to handle. He’ll face reigning Next Gen ATP Finals champion Stefanos Tsitsipas, who upset six-time titlist Roger Federer in the previous round.

“Tsitsipas is a great player. He’s playing a top level,” Bautista Agut said of the 20-year-old from Greece. “He’s one of the top players in the world. He will be one of the best, for sure. He’s playing at a very high level.”

The same can be said of Bautista Agut.