Maybe it's not too surprising that eight of those 10 teams made the playoffs. You don't make the playoffs without a solid core of excellent players. The two playoff teams not in the top 10 were the Rays, with 21.6 WAR from their top five guys (13th), and the Indians with 21.5 (14th). So, yes, stars are important.
However, it's also worth noting that most teams rated very similarly in the combined WAR from their best five players, at least in 2013: 17 teams ranked between the 22.6 WAR of the Reds and the 18.8 of the Orioles. That’s less than a four-win difference, not that four wins isn't important, but also a signal that roster spots six through 25 are often the difference between making the playoffs or heading on a fishing trip in October.
Another way to spin that is to look at the teams that received highest percentage of their overall team WAR from their five best players:
Yes, you're reading that correctly: The Astros and Phillies received more value from their top five players than they did from their entire rosters -- meaning, the rest of their rosters behind their core five were below replacement.
The main thing to take away from these "imbalanced" teams: None of them had a winning record (the Diamondbacks finished .500). The rest of the roster matters. Take a team like the Mariners. Led by Hisashi Iwakuma and Felix Hernandez, the 21.1 WAR from their top five players was on par with Rays, Indians; the rest of the roster was, collectively, horrible. Robinson Cano brings more star power to Seattle but doesn't solve the team's biggest issue, the lack of quality depth.
What about 2014? Here are my top 10 core fives heading into the season:
1. Los Angeles Dodgers
Clayton Kershaw, Hanley Ramirez, Yasiel Puig, Zack Greinke, Adrian Gonzalez
This group could be even better than it was in 2013 with full seasons from Ramirez and Puig. Greinke was so dominant over his final 16 starts (1.57 ERA) that he’s a reasonable Cy Young candidate behind his best-starter-in-baseball teammate. The fifth player on the list could be Gonzalez or Matt Kemp or even third starter Hyun-Jin Ryu.
2. Detroit Tigers
Miguel Cabrera, Max Scherzer, Justin Verlander, Anibal Sanchez, Ian Kinsler
You have the reigning two-time MVP and then two Cy Young winners and then last year's American League ERA champ in Sanchez. Kinsler will have to prove that his offensive game translates from Texas to Detroit, but his all-around game has been valuable in recent seasons.
3. Texas Rangers
Yu Darvish, Adrian Beltre, Shin-Soo Choo, Elvis Andrus, Prince Fielder
A little bit of everything: An ace pitcher, power and defense from Beltre, slick defense and speed from Andrus and two left-handed batters who get on base. The additions of Choo and Fielder help bring some lefty balance to the Rangers lineup and lead to more runs for a lineup that slipped a bit last season.
4. Pittsburgh Pirates
Andrew McCutchen, Starling Marte, Gerrit Cole, Russell Martin, Pedro Alvarez
My underrated core five. I like McCutchen to repeat his MVP season (in numbers, at least, if not in hardware), Marte and Martin to excel on defense and do just enough at the plate, Alvarez to slam 30-something homers again and Cole to become a breakout star in his sophomore season.
5. St. Louis Cardinals
Adam Wainwright, Matt Carpenter, Yadier Molina, Michael Wacha, Matt Holliday What makes the Cardinals impressive is that this core could also include Shelby Miller or Allen Craig.
Price, Myers and Cobb didn't spend the entire season on the active roster (Price and Cobb missed time with minor injuries while Myers began the year in Triple-A), so odds are strong this group could outperform last year, especially if Myers blossoms in his sophomore campaign.
A little weak in the pitching department, but Braun should return to his MVP-caliber play and Gomez was MVP-caliber in 2013. Lucroy produces at the plate and is one of the best pitch-framers in the business. Segura is an exciting plug who has to prove his second-half slump in 2013 was simply fatigue.
10. Boston Red Sox
Dustin Pedroia, David Ortiz, Jon Lester, Clay Buchholz, Shane Victorino
A good bet to regress, as a large portion of Victorino's value came from his outstanding defense and Big Papi will get old one of these years.