TORONTO -- For years, the White Sox depth chart showed left-hander Mark Buehrle atop the starting rotation. But there is a new ace in town now, and after signing a five-year contract extension in the offseason, Chris Sale is going to be around for a long time.
Now a member of the Blue Jays, Buehrle has seen several arms come and go over his 14-year career, and he believes the 24-year-old Sale has the upside to be one of the best pitchers Chicago has seen.
"He's filthy; he's a true No. 1 guy who can go out there and dominate, strike out 10-plus a game," Buehrle said before the White Sox series finale against the Blue Jays on Thursday. "You can see comparisons between him and Randy Johnson. When you're that filthy ... you can get away with a lot more than some other guys can."
Johnson, a five-time Cy Young Award winner, is one of the most dominant arms the game has seen. The left-hander made a living out of missing opposing players' bats, ranking second all time to Nolan Ryan with 4,875 career strikeouts.
Sale has a long way to go before he reaches Johnson's stature, but he's already widely considered one of the top lefties in baseball. Sale struck out 192 batters in as many innings as a 23-year-old last season, posting a 3.05 ERA.
"He's definitely one of the top arms in the league right now," Blue Jays outfielder Rajai Davis said.
Last season, Sale, a Florida native, struck out 24.9 percent of the batters he faced -- a rate topped by only Clayton Kershaw, Gio Gonzalez and Cole Hamels among left-handed starters.
After hearing what Buehrle had to say, Sale couldn't help but grin, even after coming off a loss in which he went seven strong innings against Toronto.
"It's awesome; he's one of the better ones," said Sale, who has recorded three quality starts in four outings to begin the season. "Good teammate, good person -- someone you like to have in your clubhouse, that's for sure. I like to believe I took a little bit from him while he was here."
White Sox pitching coordinator Curt Hasler said he hadn't thought about the comparison to Johnson, but he didn't blink when he heard it.
"That would be a great comparison, and I trust Buehrle," Hasler said. "[Johnson and Sale] have plus-plus stuff -- plus breaking balls -- and they're horses. Randy Johnson was a No. 1 for a lot years, and Chris can be that as well."
Sale broke into the big leagues in 2010 as a reliever before making the switch to the rotation last season. Now, pitching for a team that features a highly respected veteran in Jake Peavy, Sale is unequivocally the staff ace.
Sale had experience starting at Florida Gulf Coast University, but the conversion from a relief role to the rotation at the professional level isn't supposed to be as easy as Sale made it look.
"He made the transition seamlessly," Hasler said. "It was a tremendous Draft pick by our people. Our guys saw No. 1 upside. Our scouts are tremendous."
Sale knows the added responsibilities that come with being the ace, especially after signing an extension that will pay him $32.5 million and upward of $60 million if two club options are picked up. But he's not letting his bank account, or his designation as Chicago's No. 1 starter, get to his head.
"I don't really like to put a lot of pressure on myself, or you're kind of putting yourself in a corner," Sale said. "I just go out there and do everything I can, compete as hard as I can compete and leave everything out on the field. Whatever that equals out to at the end of the day, I can live with that."
It's that type of humility that Buehrle says is so endearing.
"He's a great kid who has a good head on his shoulders," Buehrle said. "He's not a cocky guy. He goes out there and goes about his business."
And while Sale won't admit it, White Sox manager Robin Ventura said the lefty wants to be the top dog.
"He cares a lot about the guys he plays with and to be that guy [No. 1 starter]," Ventura said. "Some people don't want to be that guy, and he wants to be that guy.
"His desire to be the starter, a No. 1 type of guy, I think the older guys that are here that are on the staff, they have kind of helped him along, as far as his development."
Ventura is not going to get caught up in lofty comparisons, but he won't dispute the assertions made by Hasler and Buehrle.
"I don't think Chris necessarily throws as hard as consistently ... but the angle, everything else he creates, the slider is very similar," Ventura said. "Angle-wise, being tall and skinny and left-handed, there is a natural comparison."
Sale can light up the radar gun with mid-90s fastballs, has devastating break on his slider and throws a strong changeup.
Sale's future is bright -- and with the White Sox. There doesn't appear to be much that can stop the left-hander from chasing down Cy Young Awards of his own, while striking out scores of batters along the way, just like Johnson.
"He's pretty filthy," Buehrle said. "You see the numbers he threw up last year. He's going to be at the top of the rotation for a while."
Chris Toman is a contributor to MLB.com.