Azarenka seized the opportunity, consolidating the break in the next game before cruising to the finish line to reach her first final in more than three years.
"I'm very pleased with how I played today," she said in an on-court interview on a warm night in northern Mexico.
"It was an important match and to see how I can do under pressure against a top player," she said.
"I haven't won many of those in the last couple years so it's good that I'm able to turn it around and pick up my level."
Earlier, second seed Muguruza eased past Slovak Magdalena Rybarikova 6-2 6-3 to book her ticket to the final.
Azarenka came out the victor in her only previous meeting with Spaniard Muguruza, a hard-fought 7-6(6) 7-6(4) win on the hard courts in Miami in 2016.
(Reporting by Rory Carroll; Editing by Amlan Chakraborty)
