Paris (CNN) Marin Cilic describes himself as a "thinker." Deeply reflective, the Croatian is one of only three players outside the Big Four to win a grand slam in the last decade and he's very conscious of not wanting to stop at one.

Don't be surprised, either, if the ongoing grass-court swing is where Cilic turns his season around after a right-knee injury heavily contributed to his ranking slipping to a five-year low.

"I understand that this year hasn't been a great one for me," Cilic told CNN Sport. "It's a challenging season but I'm still very positive in terms of my game. I feel my game is there and I just have to unlock it in a couple of good events.

"I'm feeling that the second part of the season could be a really good one. Fingers crossed."

And in an attempt to return to his grand slam winning form or even reach "another level," the 15th-ranked Cilic -- but outside the top 50 in the calendar-year standings -- added former world No. 6 Wayne Ferreira to his entourage Sunday for his two grass events to work alongside current coach Ivan Cinkus.

Presumably the collaboration will be extended if Cilic enjoys success over the coming weeks and the South African meshes with the 30-year-old's chilled, polite demeanor -- traits that belie a massive power game aided by a 6-foot-6 frame.

Marin Cilic celebrates after winning the US Open in 2014.

"I'm at the stage of my career where I had some great coaches and I learned a lot," said Cilic, speaking before he unveiled Ferreira.

He sought someone who could "help me to get those few extra percents or has a different point of view, just looking at the game in a way where they can clearly see my game and see which areas I can develop."

Asked if he can land more majors, Cilic replied: "Yeah. I'm feeling that I'm still improving and definitely looking at my last few years, 2016, 2017 and 2018, I think I improved quite a lot."

But Cilic didn't need to be told that last year, despite finishing in the top 10 for the fourth time in the past five seasons, he lost about a dozen encounters when in winnable positions.

Big serve

When Cilic bagged the US Open in 2014 with Ivanisevic alongside, he slammed a combined 50 aces in nine sets against grand slam winners or finalists Tomas Berdych, Roger Federer and Kei Nishikori to close the event. A knockout punch.

He also seemingly struck the right balance between thinking and not overthinking on court.

Cilic disagreed with the notion he needs to play more instinctively.

"I feel I'm a thinker," he said. "I'm a person that thinks and I cannot stop thinking. But I'm also aware when I'm playing aggressive tennis, when I'm playing tennis that I don't need to think, then I'm playing also great.

"I believe though that in order for me to get to the top and play the best guys and to challenge them I also need to be able to think because if you play them without a game plan, then you don't have much of a chance."

For the most part, Cilic has struck the right balance on grass.

Indeed among active players, only that quartet of Federer, Rafael Nadal, Novak Djokovic and Andy Murray have a better winning percentage -- with a minimum 50 victories on the surface -- so no one will be discounting him from becoming just the second player in the last 13 years to retain the Queens title in London this week.

He begins his title defense Monday against one of 2019's breakthrough performers, Chile's Cristian Garin.

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With virtually no grass courts back home, Cilic vividly recalls his first experience on the surface as a junior at Roehampton near Wimbledon in 2005. His earlier junior days were spent almost exclusively on clay.

"It was funny because all the juniors when they came, including me, but maybe a little less me, were feeling comfortable on the baseline, most of them were playing for the first time on grass and they were starting to serve and volley and chip and charge," he said.

"It was funny to see how we as kids were seeing tennis on grass. But as soon as I stepped on grass, I felt extremely comfortable."

Success, disappointment on grass

Cilic won the tournament in both singles and doubles and a dozen years later -- with serving and volleying a rarity for players -- landed a date with the king of SW19, Federer, in the final.

What was meant to be a joyous occasion turned into a nightmare, however, when a blister on his left foot left him distraught and quashed hopes of adding to his grand slam haul.

Marin Cilic made the Wimbledon final in 2017 but was hampered by a left foot blister.

Cilic was a serious threat, too, especially since the year earlier at Wimbledon he led Federer by two sets and even held three match points prior to the Swiss rallying.

There were further bittersweet emotions for Cilic last year.

After saving a match point at Queens to upend Djokovic in the final, he surrendered another two-set lead at Wimbledon, to grass-court novice Guido Pella, in the second round.

"Well, I actually have great great memories of the last two seasons," said Cilic. "Going out of Wimbledon last year early was definitely disappointing and just after that, it took me a couple of weeks to get back on track and in training mode. It was extremely disappointing because I felt I was in incredible form and maybe played the tennis of my life.

"But definitely I'm positive in terms of looking ahead. I'm coming back to the grass court season knowing I played so well in these last two years."

It was shortly after Wimbledon where plans were hatched by Cilic to organize a fundraiser through his charity foundation.

A year after making the Wimbledon final, Marin Cilic lost in the second round at SW19 after having a two-set lead against Guido Pella.

"Game, Set, Croatia" was held in Zagreb last week, raising money to build sports facilities for children.

A packed house of 2,000 fans looked on as Cilic and about 30 of Croatia's top athletes -- including several members of the country's side that reached the football World Cup final last year in Russia -- contested a doubles exhibition.

Charity day

Cilic partnered Real Madrid superstar Luka Modric but as it turned out, they were outdone by Juventus' Mario Mandzukic.

"Luka is really, really good," said Cilic, recipient of the Arthur Ashe Humanitarian Award three years ago. "He's got great anticipation and great feeling. He had incredible shots. But I have to also mention Mandzukic, who won the tournament with a junior from Croatia.

How about a 👏 for the @cilic_marin Foundation's successful 'Game, Set, Croatia' event, as Cilic was joined by @lukamodric10 and many 🇭🇷 stars to raise funds in order to build a sports playground for elementary school children. — ATP Tour (@ATP_Tour) June 15, 2019

"We lost in the final to them but I have to say that we are better and were supposed to win, but anyway we will take the trophy next year," Cilic added with a laugh.

In the near future, he would take the trophy next month at Wimbledon.