The biggest surprise for the Blue Jays has been Sierra's ability to hit the ball to all fields. Toronto manager John Gibbons previously thought Sierra was strictly a pull hitter, but that hasn't proven to be the case so far this season.
"To be honest, I didn't expect that from Sierra," Gibbons said. "From what we saw in Spring Training, I thought he was a dead [pull] hitter. But to be a good big league hitter, you have to be able to do that, you have to take some simple singles the other way to drive in runs.
"Pitchers up here have a little better command. If they make their pitches away, they kill you if you sit there and try to hook them all the time. You take your hits the other way ... it kind of changes how they have to approach you."
Sierra entered play on Friday night leading the Major Leagues in doubles this month with 10. He also ranked sixth during September with 33 total bases and had seen his average rise to .322 in 59 at-bats.
In total, Sierra had 13 extra-base hits in limited action this season, which is already three more than he had all of last year in almost three times the number of at-bats. The production also has been rather consistent, with Sierra hitting at least one double in all but three of his past 10 games entering Friday.
"I like everything I've seen," Gibbons said. "He has hit some breaking balls, too. He has struck out on some tough breaking balls that nobody was going to hit. But when they make a mistake with it, leave it in a little bit or hang it, he's right on it.
"As far as raw talent, he has as much as anybody. I like everything I've seen."
Gregor Chisholm is a reporter for MLB.com. Read his blog, North of the Border, and follow him on Twitter @gregorMLB. This story was not subject to the approval of Major League Baseball or its clubs.