For that, Cilic and Nishikori needed help from others who had done it. In Goran Ivanisevic and Michael Chang, they found their ideal coaching counterparts -- former Grand Slam champions who had similar backgrounds but also possessed attributes that they were searching for.
For Cilic, Ivanisevic was a fellow Croatian and sporting inspiration who had previously helped Cilic's career from arm's length but was now going to be hands-on in steering his game.
The 25-year-old had been coached by Ivanisevic's former coach Bob Brett and began working with Ivanisevic a year ago, when he returned to the tour from an anti-doping suspension that was attributed to a mistakenly purchased product and reduced in length. In addition to the renewed motivation Cilic got from the unsettling experience of testing positive, the new coaching arrangement has re-energized his career.
Ivanisevic's most obvious contribution has been helping Cilic with his serve, as the former Wimbledon champion had one of the most formidable deliveries in history. As Cilic struck service winner after service winner in his three-set win against Roger Federer in the US Open semifinals, including three aces while wrapping up the match, Ivanisevic said, "It's like watching myself."
But he has also had a wider effect on his younger compatriot, with his famous humor and personality helping bring some balance to the serious, hard-working Cilic.
That might be the biggest thing Ivanisevic has brought to his team, notes Cilic, the new US Open champion. He had reached the top 10 in 2010 but admits he started enjoying the game less and saw his ranking slip into the teens and 20s.
But there was more to the new mindset than that. For a tall, rangy player, Cilic had a conservative game, one Ivanisevic encouraged him to exchange for a more daring one.
"At the beginning when we started to work, we sat together and Goran told me that my game and my tennis has to be aggressive tennis," said Cilic. "I can't play too much tactically because most of the times before I was dealing too much with the tactics against players and not focusing on my game.
"It wasn't easy to change my perspective and to change completely my mindset. It took ... five, six months of the tournaments to be able to sink that into me and that I know on the court that's the right way for me to play. That was the most difficult part."
Ivanisevic agrees that the message took a while to deliver.
"[Cilic] was not very offensive before," he said. "You have to risk. If you don't risk, you don't know what can happen. So I tried to push him. He responded well. He was not easy, but this is the result."
The new coach also points to Cilic's fitness.
"He's covering the court well, and all the credit to the physical trainer; he really push him," Ivanisevic said. "But this year he push him even more and he really responded well."
At about the same time Ivanisevic and Cilic were beginning their collaboration, Chang was in the hallways at the US Open talking to Nishikori's team about coming on board. The two began working together during the offseason, with Nishikori also keeping his regular full-time coach.
Like the Croatian pair, Chang and Nishikori had a lot in common: an Asian background, a tennis childhood in the United States, small stature and striking speed. What Chang had, and Nishikori sometimes seemed to be lacking, was unquenchable competitiveness during matches and a willingness to push his limits.
As Ivanisevic did with Cilic, Chang told Nishikori to play a bigger game for bigger impact. Nishikori has said this approach is behind his rise this year, with Chang telling him to be "a little more aggressive than before and stepping more in."
"I think there are similarities there," Chang told reporters during the US Open. "There are style similarities. Obviously being Chinese, he's Japanese, there's cultural differences, but there's cultural similarities as well.
"I think mentality generally, being a little bit more on the quieter side, is something I understand a little more. So those similarities obviously make it a little bit easier to work with him and to communicate."
Despite his good five-set record, Nishikori has been frequently injured, including withdrawing from the Miami semifinals and retiring during the Madrid final this year. The 24-year-old almost didn't play the US Open either, having had a cyst removed from his right foot and not playing for three weeks. But Chang pushed the case for playing, saying, "Get through the first two matches and anything can happen."
"I gave him examples that I have known for myself and for Pete Sampras, where [we] were not quite sure if we were going to play and ended up having a great result," said Chang. "I actually ended up getting to the finals of the French in 1995 [after] almost pulling out of the tournament."
So Nishikori kept training, arrived at the US Open almost a week before for extra preparation and coasted to the second week. But Chang wasn't letting up.
"I just keep telling him, 'We're not done yet,'" Chang said. "I'm always trying to encourage him. I don't want him to be satisfied with round of 16.
"It's easy to be able to be satisfied with that, because his best result was a round of 16. Gets to the quarters, I think easy to be satisfied with that. You have the opportunity to win a Grand Slam, you have the opportunity to win your first major, you take advantage of it, and you come as best as possibly prepared as you can."
A pair of four-hour matches followed and then a four-set defeat of top-seed Novak Djokovic in the semifinals.
Despite reaching his first Grand Slam final, Nishikori didn't seem satisfied with a three-set defeat at the hands of Cilic, talking about building on his performance and having more chances.
The champion's mentality of the two champion coaches certainly had a noticeable impact on both Cilic and Nishikori at the beginning of their partnerships. A year later, it all came together at the US Open.
Along with everything else, don't discount the effect of having a former idol join a player's team. Several current players have benefited from working with well-known names this season.
The coaches get something from it too, with Ivanisevic saying that watching Cilic win was not unlike his famous Wimbledon victory and Chang citing an opportunity to do something for Asian tennis, just as his older brother Carl did for him.
"There has been only one other Asian man that has broken into the top 10, and that was Paradorn [Srichaphan]," Chang said. "Being in that 15-16 range, there was actually a fair amount of similarities because I was stuck in that range in 1990, 1991, until Carl came and coached me.
"So I felt I have an opportunity to be able to help a young, very talented Asian player be able to take his game to the next level."
The two US Open finalists knew how to play. Now, their coaches are showing them how to win.