In Game 7 of the American League Championship Series, Astros right-hander Lance McCullers was in a situation every pitcher dreams of: The ball was in his glove, and he had a chance to send his team to the World Series.
But instead of rearing back and firing fastballs, McCullers went with his high-velocity, high-spin knuckle-curveball -- not once, not twice, but 24 times in a row. It was an unprecedented reliance on a breaking ball, and the Yankees were rendered helpless.
"It's an aggression pitch for me," McCullers said of his knuckle-curve back in May. "It's called an offspeed pitch, but I don't view it that way."

The adage "work off your fastball" has been passed down to pitchers for about as long as professional baseball has existed, but the tide is changing. Dodgers ace Clayton Kershaw, arguably the game's best pitcher, just dipped his fastball usage below 50 percent for the first time in his career. Sixteen other non-knuckleball starters did the same, and four pitching staffs (Dodgers, Indians, Rays and Yankees) did not throw a majority of four-seam, two-seam and sinking fastballs (sinkers), which is the most amount of teams to not do so in a season since 2008.
More pitchers are thinking along with McCullers: If an offspeed pitch is your best weapon, why not go with it repeatedly? The curveball, slider or changeup doesn't have to be a secondary pitch if opponents simply can't hit it.
That approach might not be for everyone, but below are five starters who may want to experiment with a heavier dose of "secondary" pitches, based on some terrific Statcast™ metrics in their favor. 
Scott Feldman: Curveball
Feldman's 4.77 ERA and 5.04 Fielding Independent Pitching in 2017 for the Reds were below average, and opponents fared well against his sinker (.277 average, .527 slugging) and his cutter (.336 average, .541 slugging). But Feldman's curveball was dominant. Only five starters allowed a lower average exit velocity on curveballs than Feldman at 81.7 mph, and only four (including Jerad Eickhoff) allowed a lower hard-hit rate.
Feldman's curveball has improved over the past three seasons, culminating in a .133 average bested by only three other starters in 2017. Feldman threw his hook about a quarter of the time last year, and the free agent could be well served by throwing it even more going forward.
Eickhoff: Curveball
Eickhoff's four-seam fastball was one of the 15 slowest among MLB starters at 90.4 mph, and it got hammered for a .316 average and a .497 slugging percentage as he featured it nearly 40 percent of the time. The Phillies right-hander's two-seamer fared even worse, yielding a .400 average to opponents that ranked among the worst in the Majors.

Eickhoff's curveball was a different story. Opponents made hard contact (defined by Statcast™ as any ball hit with a 95-mph exit velocity or harder) on only 14 percent of their batted balls against Eickhoff's hook, fifth lowest among 71 pitchers who induced at least 50 batted balls on curves. They whiffed on a third of their swings against his curve, a top-20 rate among starters, and hit just .169 vs. the pitch. Eickhoff ticked up his curveball usage in each of his first three years -- up to 32.3 percent in 2017 -- but perhaps he could ramp it up even more in '18.
Mike Leake: Slider
The Mariners right-hander will always be a guy whose game plan is to make batters hit ground balls, and his sinker is integral to that plan. Still, Leake allowed a .329 average on his sinker last year, even while opponents were hitting it for grounders more than 60 percent of the time. Meanwhile, those batters hit only .181 against Leake's slider, the same mark as D-backs breakout left-hander Robbie Ray.
Statcast™ says Leake's slider should have fared even better, as his .168 expected batting average -- based on quality of contact and real-life strikeouts -- ranked among the top 15 starters in the Majors. Leake featured his slider only 13.4 percent of the time, and it's worth wondering if he could build on a solid 2017 by featuring that pitch even more next year.

Sean Manaea: Slider
Manaea's season went into a tailspin after he encountered a period of extreme weight loss stemming from medicine he was taking for Attention-Deficit Disorder (ADD). His velocity dipped as a result, but with the medical issue hopefully resolved, the A's prized young lefty should be back at his ideal weight in 2018. Even through his sophomore struggles, Manaea's slider flashed plenty of potential. Opponents hit .174 against the pitch and, more importantly, righties fared even worse at .149.
Manaea's slider plays well off the fastball and changeup from his wide release point, and it can neutralize the platoon advantage as it nips at a right-hander's ankles, but he threw it less than 20 percent of the time in 2017. Manaea admitted that he's still looking for the complete feel of his breaking ball, and he was fastball-dominant last season. But with full health and more trust, Manaea's slider could become a real weapon.

Edinson Volquez: Changeup
Volquez struggled much of the year with his fastball command, recording one of the lowest strike rates on heaters of any starter in 2017. But Volquez's changeup has been a plus pitch for a while, and it elevated to another level last year. Astros ace Dallas Keuchel is the only starter who allowed a lower average exit velocity on changeups than Volquez at 79.8 mph, and the Marlins right-hander did not allow a single barrel (a ball hit with an optimal combination of exit velocity and launch angle) out of the 71 balls put in play off his change-of-pace pitch.
Opponents managed only 17 hits in 103 at-bats ending with a Volquez changeup for a .165 average that slotted among the 10-best starters in the game.
Volquez went changeup a quarter of the time last year, making it his No. 2 option. He might not make the change his primary pitch, but there's an argument for throwing it even more.