"I'm not looking back 2017 any more", Kerber, who won the Australian Open and the U.S. Open titles in 2016, said.
"It's nice to make a final at home, but I think in my eyes it's flawless preparation for next week", Barty said after her win.
She will meet the victor of another quarterfinal between defending champion Agnieszka Radwanska and qualifier Camila Giorgi.
"Being now in the semis again here, it's really a good feeling, especially that I had the goal, to have a lot of matches before going to Melbourne".
Italian qualifier Camila Giorgi continued her impressive run at the Sydney International by racing past Agnieszka Radwanska 6-1 6-2 on Thursday to set up a last four clash with Angelique Kerber.
Kerber, who began a year ago as No.1 before finishing at No.22, continued her 2018 resurgence with a thumping 6-3, 6-1 win over Slovakia Dominika Cibulkova.
It's just the beginning of the year.
Australian Ashleigh Barty also advanced to the semifinals with a 6-3, 6-2 win over Barbora Strycova.
"To be honest, I felt like I probably played some of the better tennis that I have this week".
The Queenslander won 3-6, 6-4, 6-2 against a fiery Gavrilova, who struggled to find any consistency with her serve, and who earned a code violation for racquet abuse when frustrations boiled over.
"I feel like I can fly under the radar a little bit more maybe than other years, but when you are playing well and have that better number next to your name, that is obviously a great thing". "I love playing in Australia, I love playing at home".
The 84th-ranked Medvedev came back from a set down to move within one win of what would be his maiden ATP title against rising Australian star Alex de Minaur.
Russian qualifier Daniil Medvedev upset Italian fourth seed Fabio Fognini 2-6, 6-4, 6-1 to reach the Sydney men's final.
Paire sent down 17 aces against the world No.25 to advance to his second semi-final in a week, after reaching the last four in India.