Garbine Muguruza advanced to the championship match of the WTA Finals with a 6-3, 6-3 win over fellow Spaniard Paula Badosa in Guadalajara, Mexico, on Tuesday.
Muguruza, who will end the year ranked world number three, will face Estonian Anett Kontaveit in Wednesday's final.
Kontaveit downed Maria Sakkari of Greece 6-1, 3-6, 6-3 in the second semifinal.
In their first career meeting, Muguruza's superior firepower put Badosa on the back foot from the outset and she broke the Indian Wells champion for a second time with a forehand winner to take the first set.
Badosa's frustration boiled over during the change over and she was unable to hold serve in the lengthy second game of the second set, giving the former world No. 1 and two-time Grand Slam champion another early break.
Muguruza fended off Badosa's three break point chances in an 11-minute third game to take a 3-0 lead and rolled on from there, firing an ace to go up 5-2 and sealing the win when Badosa hit a backhand into the net on match point.
"I think it's the best match that I played so far here in Guadalajara," Muguruza said.
"It was a tough match facing another Spaniard in the semifinals of a Masters. Actually the first time we've encountered together ... so it was tricky.
"But I'm very happy that I got the win."