Rafael Nadal's stirring Grand Slam revival faces a threat from the in-form Grigor Dimitrov as he attempts to reach his first major final in two-and-a-half years at the Australian Open.
The 30-year-old Spaniard has been out of the Grand Slam limelight since his last title success at Roland Garros in 2014, as injuries sidetracked his once-glorious career.
But victory over Bulgaria's 15th seed Dimitrov, once dubbed 'Baby Fed', on Friday in the second men's semi-final will put Nadal one win away from a 15th major title.
However, Dimitrov is enjoying some of the form of his life coming into what will be his first major semi-final since Wimbledon in 2014.
Dimitrov, five years younger than Nadal, was once hailed as a future champion and nicknamed 'Baby Fed' owing to his Roger Federer-style court movement and single-handed backhand.
After his upset of defending champion Andy Murray at Wimbledon in 2014 he lost to Novak Djokovic in the semis, reaching number eight in the rankings. But after that, his career failed to take off.
Now under Murray's former coach Daniel Vallverdu, Dimitrov is unbeaten in 2017, winning his fifth career title in Brisbane and now on a run of 10 matches without defeat.
While Federer has enthralled the tennis world with his comeback from an injury-blighted 2016, so too has Nadal's charge through the bottom half of the draw.
He has looked like the Nadal of old as he tossed aside Alexander Zverev, Gael Monfils and Milos Raonic to be just one step away from his fourth Australian final.
Nadal has added Carlos Moya to his coaching team and since his first-round loss to Viktor Troicki in Shanghai in October he has worked hard to get his game into shape.
"It's good news, especially winning against difficult players: Monfils in quarter-finals, Zverev round of 16, and Raonic," Nadal said.
"All of them are top players. So that's very important for me because that means that I am competitive and playing well. I worked hard to try to make that happen."
Nadal is now dialled in for his next challenge presented by the increasingly impressive Dimitrov. The winner will play Federer or Stan Wawrinka in Sunday's final.
"He's a player that has an unbelievable talent, unbelievable potential. He's started the season playing unbelievable," Nadal said of Dimitrov.
"It's going to be a very tough match for me. I hope for him, too. I have to play my best because he's playing with high confidence."
The 2009 winner is 7-1 in his matches with Dimitrov, including a four-set quarter-final win at the Australian Open three years ago.
Another salient statistic is that Nadal is 66-8 against players with one-handed backhands at Slams.
Dimitrov is confident of his chances and in the first week of this season he accounted for three top-10 opponents – Dominic Thiem, Raonic and Kei Nishikori – on the way to winning the lead-up Brisbane International tournament.
The last time the Bulgarian won 10 straight matches was back in 2014, when he took the title at Queen's and reached the last four at Wimbledon.