The MLB playoffs are over so let’s take a minute to look back on them. What makes the playoffs so interesting is that it’s such a small amount of games compared to the regular season and those games decide everything. For this reason, the best players in the regular season, aren’t the best players in the playoffs. The best players in the playoffs are the players who increase their team’s chances to win the World Series the most. This can be measured by cWPA (championship win probability added). Regular WPA measures the increase or decrease of a play in the team’s chance to win the game and gives credit to the player at bat or pitching. Then there’s cWPA, which measures how much the play increases or decreases the team’s chances of winning the World Series. Below is a table of the top 10 players in cWPA for the 2018 postseason.
| Pos | Team | Player | cWPA |
| RF | LAD | Yasiel Puig | 0.223 |
| 1B | BOS | Steve Pearce | 0.220 |
| 3B | BOS | Rafael Devers | 0.143 |
| RP | LAD | Pedro Baez | 0.132 |
| RP | MIL | Josh Hader | 0.128 |
| CF | BOS | Jackie Bradley Jr | 0.126 |
| RP | MIL | Corey Knebel | 0.122 |
| RP | BOS | Craig Kimbrel | 0.119 |
| RP | BOS | Matt Barnes | 0.100 |
| CF | HOU | George Springer | 0.097 |
The chart below shows the regular season top 10 in WPA for players on the Red Sox, Astros, Dodgers and Brewers.
| Pos | Team | Name | WPA |
| RF | MIL | Christian Yelich | 6.02 |
| 3B | HOU | Alex Bregman | 5.94 |
| RF | BOS | Mookie Betts | 5.77 |
| DH/OF | BOS | J.D. Martinez | 5.24 |
| RP | MIL | Jeremy Jeffress | 4.85 |
| SP | HOU | Justin Verlander | 4.7 |
| SP | BOS | Chris Sale | 4.06 |
| LF | BOS | Andrew Benintendi | 3.81 |
| RP | BOS | Craig Kimbrel | 3.66 |
| SS | BOS | Xander Bogaerts | 3.63 |
The only player that occurs on both is relief pitcher Craig Kimbrel. This only reinforces how the top regular season hitters aren’t the top in the playoffs. The playoffs are a weird time because we know who will pitch the important relief innings. Those guys are on this list, but for hitters, no one really knows. The most important hitters were Yasiel Puig, Steve Pearce and Rafael Devers. This is why it can be so difficult for teams adding at the trade deadline. If you know you will be in the postseason, you’re better off adding solid bullpen arms that you know will have important innings. Position players can add value and help a team get to the playoffs like Manny Machado did, but it is difficult to count on anything from certain hitters in the playoffs. Machado was among the worst in the playoffs. The table below shows the worst 10 players in the 2018 playoffs in terms of helping their team win a World Series.
| Pos | Team | Player | cWPA |
| OF | LAD | Enrique Hernandez | -0.182 |
| RP | MIL | Jeremy Jeffress | -0.175 |
| SS | LAD | Manny Machado | -0.111 |
| CF | LAD | Austin Barnes | -0.107 |
| SS | BOS | Xander Bogaerts | -0.102 |
| 1B/CF | LAD | Cody Bellinger | -0.098 |
| C | LAD | Yasmani Grandal | -0.086 |
| RF | MIL | Christian Yelich | -0.085 |
| C | BOS | Christian Vazquez | -0.084 |
| CF | LAD | Joc Pederson | -0.081 |
Manny Machado and Christian Yelich appear on this list, which only further proves how unpredictable hitters can be in the playoffs. Jeremy Jeffress appears as the one reliever who had a really rough postseason. This is why there is so much emphasis on acquiring pitchers and bullpen arms for playoff teams. Sure some guys like Jeffress could struggle, but for the most part guys like Josh Hader for Milwaukee and Pedro Baez for the Dodgers will be guys who you lean on game in and game out.
Below are listed the top five plays for cWPA this postseason.
| Rk | cWPA | Play | Pitcher | Game | Inn | Outs | Score |
| 1 | 0.13 | Puig: 3-Run Home Run | Jeremy Jeffress | NLCS Gm 7 | ↑6 | 2 | 2-1 |
| 2 | 0.11 | Devers: Single to CF | Dylan Floro | WS Gm 4 | ↑9 | 1 | 4-4 |
| 3 | 0.10 | Puig: Single to 2B | Nathan Eovaldi | WS Gm 3 | ↓13 | 2 | 1-2 |
| 4 | 0.09 | Pearce: Solo Home Run | Kenley Jansen | WS Gm 4 | ↑8 | 1 | 3-4 |
| 5 | 0.09 | Bellinger: 2-Run Home Run | Jhoulys Chacin | NLCS Gm 7 | ↑2 | 0 | 0-1 |
The single most influential play was the Yasiel Puig 3-run homer off Jeremy Jeffress in Game 7 of the NLCS. Puig is also third on the list with his 13th inning game tying single in game 3 of the World Series. I’m not sure that it really tells us a whole lot that these particular guys were clutch, but it’s intriguing to see what plays mattered the most in this postseason.