After a sensational second half in 2018, and a fantastic first half in ‘19, what’s next for Christian Yelich? An unprecedented baseball feat is one looming possibility.

Forty men throughout Major League history have paired 30-plus homers with 30-plus stolen bases, in a satisfyingly symmetrical combination of power and speed. Only four of those have gone 40-40 -- Barry Bonds, Jose Canseco, Alex Rodriguez, and Alfonso Soriano.

None has managed a combo that is less uniform but no less impressive: 50-30.

Yelich just might change that. Before starting Tuesday’s All-Star Game in Cleveland for the National League, he had bashed an MLB-high 31 homers and tied for fourth with 19 stolen bases over the Brewers’ first 91 games. He’s the only player ever to go 30-15 in the first half.

Yelich hasn’t even played that whole schedule, missing nine games mostly due to back issues. But extrapolating his pre-break numbers over 162 games yields 55 home runs and 34 steals -- a never-before-seen display of strength and speed.

Baseball, in its unforgiving way, rarely looks kindly upon such assumptions. But who can doubt Yelich at this point?

Traded from Miami to Milwaukee before last season, he arrived as a player who had demonstrated considerable value -- averaging 4.3 WAR, per Baseball Reference, from 2014-17 -- but who had not produced the sorts of gaudy stats that draw a lot of attention. Toiling for the Marlins, Yelich’s career highs in homers and steals were both 21, though not in the same season.

Before the 2018 All-Star break, it looked like more of the same steadiness, as Yelich posted an .823 OPS with 11 homers. He’s been an unstoppable force at the plate ever since, driving the ball in the air more and taking advantage of a homer-happy environment. The 27-year-old outfielder slashed .367/.449/.770 with 25 long balls after last year’s break, and has silenced talk of a fluke by slashing .329/.433/.707 with 31 dingers so far this year.

Any consideration of Yelich’s 50-30 chances have to take this into account: In his past 156 games since last July 8, he has smacked 56 homers and swiped 31 bags (If Yelich plays in every remaining Brewers game, he will finish with 153 this year).

Of course, Yelich isn’t the first player to make a run at 50-30. Nine players have reached 40 homers while stealing at least 30, and four have reached 20 steals while going deep at least 50 times. Here is a look at those who came the closest:

Most HR in a 30-SB season

1. Larry Walker (1997 Rockies): 49 HR, 33 SB
2. Alfonso Soriano (2006 Nationals): 46 HR, 41 SB
3. Hank Aaron (1963 Braves): 44 HR, 31 SB
4. Jeff Bagwell (1997 Astros): 43 HR, 31 SB
5. Jeff Bagwell (1999 Astros): 42 HR, 30 SB

Walker was the NL MVP in 1997, when he actually hit 29 of his 49 homers away from Coors Field. Soriano missed a 50-40 season with a slow finish that saw him hit just two homers in his final 26 games. Aaron reached 30 steals just once in his career, and paired it with one of his eight 40-homer campaigns. Bagwell is the only first baseman in history to go 30-30.

Most SB in a 50-HR season
1-T) Alex Rodriguez (2007 Yankees): 54 HR, 24 SB
1-T) Willie Mays (1955 Giants): 51 HR, 24 SB
3) Brady Anderson (1996 Orioles): 50 HR, 21 SB
4) Ken Griffey Jr. (1998 Mariners): 56 HR, 20 SB

Perhaps not surprisingly, 50-homer power traditionally has not mixed with high steal totals. Rodriguez, Mays and Anderson all stole 30-plus bases in other seasons, although not in these big power years. Mays actually stole at least 30 every year from 1956-58, but with a corresponding drop in homers.

These examples suggest the difficulty of sustaining both a 50-homer pace and a 30-steal pace over a full season. Even if Yelich avoids further back trouble and stays on the field, the odds might be against him avoiding a slump in one category or the other. And it’s worth considering that two prominent projection systems available at FanGraphs -- ZiPS (47 HR, 29 SB) and Steamer (46 HR, 28 SB) -- both have Yelich falling short.

Then again, such a pursuit would have seemed impossible just one year ago. Yelich is a different player now, and soon he just might be one of a kind.