Roger Federer described his Australian Open semi-final victory as "bittersweet" after Hyeon Chung retired due to blisters on his left foot.
Federer dominated the unseeded South Korean on Rod Laver Arena, ruthlessly cruising into a 6-1 5-2 lead under the roof on Rod Laver Arena before a one-sided match came to a premature end.
The defending champion outclassed Chung and looked set for a crushing straight-sets victory, but the Next Gen ATP Finals champion decided he was unable to continue when on the brink of going two sets down.
Nineteen-time grand slam winner Federer will play Marin Cilic in a showdown on Sunday, yet he was left with mixed feelings after reaching his 30th major final.
The second seed said: "In the second set I could see he was starting to get slower, fighting with the blister.
"It's bittersweet to reach the final in this way. I'm incredibly happy to be in the final, but not like this.
"I could tell something was wrong before he took the timeout [taken when Federer led 4-1]. But he has a great composure and I think we're going to see a lot more for him, top 10 for sure.
"The rest, I don't know, I don't want to put too much pressure on him. I think he's going to be a great player."
Federer beat Cilic in straight sets in the Wimbledon final last year, the Croatian reduced to tears as he also struggled with blisters, but the world number two is expecting a closer encounter at Melbourne Park.
"We saw it against Rafa [Nadal] and we saw it again last night against [Kyle] Edmund. He brings power, basically everything. He had the same problem as Chung had in the Wimbledon final," said the 36-year-old maestro.
"We will see a fresh and ready Marin this time around. He has the power, and if he's come this far he's playing well."