Federer, who will be playing in his 30th major tournament final, will face Cilic in the 2018 Australian Open men's singles final on Sunday in a rematch of the 2017 Wimbledon final.
Federer is 5-1 in Australian Open finals, with his most recent championship coming a year ago over Rafael Nadal.
Cilic is entering his third major tournament final on Sunday at Rod Laver Arena in Melbourne, Australia. He won the 2014 U.S. Open against Kei Nishikori and fell to Federer last year at Wimbledon.
Date: Sunday, January 28
Time: 3:30 a.m. ET
Live Stream: Watch ESPN
Cilic Looking for 2nd Career Win Over Federer
Much like everyone else on the ATP Tour, Cilic has a losing record against Federer.
Cilic's only win over the Swiss great came at the 2014 U.S. Open, as the Croatian knocked off Federer in the semifinals in straight sets on the way to his only Grand Slam title.
The closest Cilic has come to beating Federer since then was the 2016 Wimbledon quarterfinals, as he took the 19-time major winner to five sets.
No matter what he achieves on Sunday, Cilic has already boosted himself up to third in the ATP world rankings, placing himself right behind Rafael Nadal and Federer, as Christopher Clarey of the New York Times noted.
Cilic is vying to become the first Croatian men's tennis player to win multiple Grand Slam championships. Goran Ivanisevic is the only other Croatian male to win a major title.
The 29-year-old is also the first Croatian to reach an Australian Open final, per the tournament's official Twitter account.
Although he's faced a tougher road to Sunday's championship match than Federer, Cilic is feeling confident in his game.
"I'm feeling that I am, for most of the shots, hitting them really, really good," Cilic said, per ESPN's Simon Cambers. "From the return, moving, forehand, backhand, serving, I think everything is in good, solid spot. Feeling really excited about the final, too."
Of course, confidence and a good run of form can only help you so much when you're taking on the greatest men's tennis player of all time.
Federer After 20th Grand Slam Title
Not even Father Time can find a way to beat Federer.
The 36-year-old hasn't lost a set in Melbourne over the last two weeks and is ready to capture his 20th Grand Slam title to add to the record few, if any, will ever have a chance at breaking.
"It's a number that I honestly didn't think I'd get to or be close to," Federer said, per Clarey. "Last year before this tournament I would have been happy to say that I'd win one more Slam before the end of my career. I'd been trying for four or five years to win one more, and I would have said, 'One more? Great!'"
Before winning the 2017 Australian Open, Federer missed out on four straight Grand Slam finals and was without a major since Wimbledon in 2012.
The Swiss legend comes into the final with fresher legs than Cilic, after being on the court for just over an hour in the semifinals before Hyeon Chung retired.
In fact, Federer has rarely been on the court for more than two hours in Melbourne; Tennis TV has provided a look at the comfortable road the No. 2 seed has had to the final.
All of the recent trends favor a 20th Grand Slam victory for Federer in his 30th final, but he knows defeating Cilic won't be an easy task, per the tournament's Twitter account.
There's a chance Federer loses his first set of the tournament on Sunday. He's lost at least one set in six of his last seven Grand Slam finals, with the Wimbledon win over Cilic being the lone exception.
Even if he drops a set, it's still hard picking against the best male player to step foot on a tennis court.
Prediction: Federer over Cilic in four sets.
Follow Joe on Twitter, @JTansey90.