I typically update my ranking of the top MLB players under age 25 once a year, but with playoff rosters loaded with young talent, a year ago I started producing a special, shorter edition highlighting the top young players on postseason teams, and I'm doing so again for another youth-infused 2018 postseason field.
I use seasonal ages here, so to be included a player had to be 24 years old or younger on July 1.
An interesting fact: The top five hitters under 25 by FanGraphs' WAR are all in the playoffs, and nine of the top 12 are either on playoff teams or a team that just missed (the Cardinals, with two). Make sure you're sitting down for this, but it turns out having very productive young hitters in your lineup appears to be a good thing for your playoff chances. Go figure.
Lindor and Bregman have quite a bit in common: Both were amateur shortstops, considered somewhat undersized and expected to hit for average but not for power, yet both reached 30 homers this year without losing anything else from their offensive profiles. Lindor is the better defensive player, a plus glove at shortstop with tremendous instincts, while Bregman has done a credible job playing out of position at third, with defensive value a little below average by defensive runs saved and UZR. They're far and away the two best under-25 players on postseason rosters, and you could pick either to be No. 1 overall, but I'd give the nod to Lindor because of how much he contributes in the field and the difficulty of finding that kind of offensive production from a shortstop.