Atlanta United secured their place in the MLS playoffs with a 4-1 win over Montreal at Mercedes-Benz Stadium on Saturday but D.C. United's hopes suffered a blow with a 5-3 defeat at home to the New York Red Bulls.
Eastern Conference leaders FC Cincinnati showed why they are one of the favorites for this year's title with a wonder goal from Argentine Luciano Acosta in a 3-0 defeat of Charlotte.
Five of the playoff spots in the East have now been booked with fifth-placed Atlanta joining the Philadelphia Union, Columbus Crew, Orlando City and Cincinnati in the post-season berths.
The top seven teams in each conference head straight into the best-of-three first round series with the eighth and ninth placed team battling it out in the wildcard round for the last spot.
Atlanta, the 2018 MLS champions, took a 30th minute lead through Portugal's Xande Silva and three minutes later Argentine World Cup winner Thiago Almada doubled the advantage, tapping home after more good work from Silva.
Ahmed Hamdi pulled a goal back for Montreal with a sweet strike from the edge of the box just before the break but Atlanta restored their advantage right after the restart when Greek forward Giorgios Giakoumakis chipped home after some sloppy defending from the Canadian side.
Montreal's task got tougher when Joel Waterman was harshly sent off for a last man foul, after the slightest touch on Jamal Thiare, and Edwin Mosquera wrapped up the win for Atlanta after being set up by Almada.
Wayne Rooney's D.C. United are hanging on to ninth place but the New York Red Bulls moved within two points of them after winning an eight-goal thriller at a drenched Audi Field.
After a pre-game downpour, Belgian former Premier League forward Christian Benteke scored a first-half hat trick for D.C. but had to head in at the break on level terms after Cameron Harper equalized for the Red Bulls just before the half-time whistle.
Sean Nealis headed New York in front in the 58th minute after being left unmarked in the box and then John Tolkin made sure of the three points in stoppage time.
Cincinnati are leading the race for the Supporters' Shield, awarded for the team with the best regular season record across both conferences, after their latest impressive performance inspired by two Argentines.
Alvaro Barreal broke the deadlock before the break with a brilliantly whipped left-foot free-kick and then his compatriot Acosta set up Aaron Boupendza for the second.
Acosta, who signed a new deal with the Ohio club on Friday, sealed the victory with an outstanding solo goal, picking up the ball on the half-way line and dribbling past three Charlotte defenders before blasting home.
The re-match of last year's MLS Cup final between the Philadelphia Union and Los Angeles FC ended goalless in Pennsylvania.
Philadelphia, seeking revenge for their loss in L.A., thought they had the lead in the 50th minute but Daniel Gazdag's header was chalked off for offside after a VAR review.
Later on Saturday, St.Louis City, the only team in the West to have qualified for the playoffs, travel to Minnesota.
On Sunday, Inter Miami, without the injured Lionel Messi, continue their playoff push at Florida rivals Orlando.