The 5-foot-11 outfielder hit a two-run walk-off triple on Saturday to lead Salt River to a 5-4 victory over Mesa in Arizona Fall League action.
"He first threw me a two-seem fastball outside," said Fields, Toronto's No. 22 prospect, recounting the at-bat. "It was low. He was trying to get me to hit something on the ground. And then I was trying to look for something I could drive, no matter what side, and he threw a pitch almost right down the middle and I turned on it."
Fields has had quite the career already, going undrafted out of Kansas' Bethany College in 2013. He returned home to the Pacific Northwest, thinking his career was over, before being seen by scouts in a tournament.
He was signed in August 2013 as a non-drafted free agent and reached Double-A in 2015, a year after he set a record for the Vancouver Canadians in the short-season Northwest League with 48 stolen bases.
He made it to Triple-A Buffalo this season, combining to slash .262/.316/.321 in 121 games over three Minor League levels.
"Just to prove that I can play at this level and contribute," Fields said of his Arizona Fall League goals. "Doesn't matter where you've come from, if you've been drafted or not. You can play the game."
Spencer Kieboom led Salt River with three hits, while Raimel Tapia was 2-for-4.
Chad Henshaw led Mesa with four hits from the leadoff position, while Renato Nunez, Casey Gillaspie and Daniel Robinson had two each.
Cash Kruth is a reporter for MLB.com. Follow him on Twitter at @cashkruth. This story was not subject to the approval of Major League Baseball or its clubs.