MLS Cup playoffs 2021: New England Revolution, Seattle Sounders heavy favorites. Atlanta United, Nashville SC among dark horse teams.

The 2021 MLS Cup playoffs kick off Saturday with two games: New York Red Bulls at Philadelphia Union (2:30 p.m. ET on Univision/TUDN) and Vancouver Whitecaps at Sporting Kansas City (5 p.m. ET on UniMás/TUDN). 

The action continues with two games Sunday – Atlanta United at New York City FC (3 p.m. ET on ABC) and Minnesota United at Portland Timbers (5:30 p.m. ET on ESPN - and two more on Tuesday – Orlando City SC at Nashville SC (8 p.m. ET on FS1) and Real Salt Lake at Seattle Sounders (10:30 p.m. on FS1).

The 14-team playoffs will culminate with MLS Cup on Dec. 11 (on ABC). 

USA TODAY Network's team of soccer experts make their predictions for which teams could reach and ultimately win MLS Cup, which teams are dark horse contenders and the biggest X-factor players heading into the postseason.

How we see the MLS playoffs going down:

MLS Cup predictions

Pat Brennan, Cincinnati Enquirer: New England Revolution over Seattle Sounders. Even with the unbalanced scheduling, New England was head and shoulders above its MLS peers in 2021. Are they the hottest team going into the playoffs and peaking at the right time? Maybe not the hottest club, but that won’t matter for two reasons: They clinched the Supporters' Shield and the single-season points record with matches to spare, and the international break will have disrupted the rhythm for all MLS clubs. Seattle is going back to MLS Cup and should have a hint of extra motivation after it was passed by the Colorado Rapids for the No. 1 spot in the West. 

Drake Hills, The Tennessean: New England Revolution over Seattle Sounders. This game will be a chess match between New England’s Bruce Arena and Seattle’s Brian Schmetzer, meaning I don’t see many giveaways on what will inevitably be a stiff, plastic turf surface on a brisk night. Raúl Ruidíaz will score the lone goal for the Sounders, but Tajon Buchanan and Gustavo Bou will double up to give the Revs the win and the MLS Cup trophy. 

MORE FROM DRAKE HILLS:Predicting every playoff Round 1 matchup and an MLS Cup champion

Jacob Myers, The Columbus Dispatch: Sporting Kansas City over New England Revolution. New England is the obvious favorite, but Sporting has made life difficult for the best teams in MLS all season. Motivated by a loss in the conference semifinals last season as the No. 1 seed, Kansas City has experience and goal scorers in Dániel Sallói and Johnny Russell to finish the job this time.

Jim Reineking, USA TODAY Sports: Seattle Sounders over Nashville SC. History has not been kind to Supporters' Shield winners; only four in the past 20 years went on to win MLS Cup. That math does not add up for the New England Revolution, the team that finished with the league's best record and set a new season points record. The international break should serve the Sounders well, with Jordan Morris and Nico Lodeiro each recently returning from injuries. Nashville made an inspired run in the playoffs last season, and bring a more formidable team to this year's postseason tournament. 

MLS CUP PLAYOFFS 2021:Live stream, game times and dates, odds, how to watch

MLS CUP:Ranking every Major League Soccer championship game

Dark horse MLS Cup contenders

Pat Brennan: Philadelphia Union. The Union did seem to be a club that peaked at the right moment going into the international break, as evidenced by the fact that they sneaked past Nashville SC for the No. 2 spot in the Eastern Conference. And maybe the No. 2 and last year’s Supporters' Shield winner shouldn't qualify as a dark horse, but Philly will have revenge on its mind after bowing out in the first round of the playoffs last year. The Union also qualify as "dark horses" for me because they’ve been so hot and cold at times in 2021.

Drake Hills: Atlanta United FC. I watched newcomer Luiz Araújo in just his third match as an Atlanta United player in August, going up against Nashville SC. Still unsure of what to expect from Ezequiel Barco as a prime-time player, the Brazilian Araújo is the spark Atlanta needs to partner with Josef Martinez and make a run in the playoffs as the No. 5 seed in the East.

Jacob Myers: Nashville SC. Yes, Nashville seems impossible to lose to. But they're also nearly impossible to beat. Don't overlook this team that only lost four games all season and has enough weapons to get enough goals to win the whole thing.

Jim Reineking: Portland Timbers. Portland's road to the Western Conference final includes a home game against Minnesota United followed by a road game against the Colorado Rapids (on Thanksgiving!). This seems like a doable proposition for a Portland team that could be highly motivated in what might be team legend Diego Valeri's final MLS season.

MLS playoff X-factors

Pat Brennan: Valentín Castellanos, New York City FC. "Taty" Castellanos, the 2021 Golden Boot winner, could throw a real wrench into the Eastern Conference side of the MLS Cup playoff bracket. NYCFC hosts Atlanta United in the first round and would then advance to play New England. Castellanos has the ability, he's a big-match player and would be a tough out for the Revolution if he hits the ground running against Atlanta. 

Drake Hills: Carles Gil, New England Revolution. Any time a player can generate more than 100 key passes, like the Spaniard Gil did despite missing August entirely due to injury, their impact on a team in the attacking third is undisputable. It’s likely that Gil will win the Landon Donovan MLS MVP Award. He’s got a whopping 18 assists and two strikers, Adam Buksa and Bou, to turn to. If Gil is at his best, it will be hard for anyone to stop New England.

Jacob Myers: Hany Mukhtar, Nashville SC. Maybe there's an Eastern Conference bias here, but I'm buying what Nashville has been putting down this year. If Mukhtar can be the MVP-caliber player he has been through most of this season, it'll be difficult for any team to knock out this club that has yet to open its own stadium.

Jim Reineking: Jordan Morris, Seattle Sounders. Morris played in two regular-season games for a total of 75 minutes after recovering from an ACL injury suffered on Feb. 20 while on loan at Swansea City of the English Championship. For what was one of the league's best teams all season long, Morris' addition is like the rich getting richer. Morris most likely will make an impact in a super-sub role.