[12] MLS continued to use the modified version of the sport's rules that it adopted for the 1996 season, including a penalty shootout from 35 yards (32 m) to decide tied matches (for which the winners earned one point) and a countdown clock that stopped during dead plays.

[18] The two teams participated in the expansion draft, where Chicago selected two players from the Los Angeles Galaxy who were later traded back in exchange for goalkeeper Jorge Campos and midfielder Chris Armas.

[24][25] Chicago's offensive pair of Nowak and Kosecki were also frequent targets of fouls, picking up injuries and suspensions during a loss to D.C. United in early May that elicited complaints from manager Bob Bradley over missed calls from the referee.

[27] The streak included consistent scoring from Nowak, who was named Player of the Month in May, and several shutouts from goalkeeper Zach Thornton, who would be competing for the starting position with Campos.

[29] Chicago were unable to surpass the Galaxy in the standings, but were able to open a 18-point lead over the third-place Dallas Burn by defeating them three times in a three-week period by early July.

[22] The team remained in second place and eight points ahead of third-place Colorado by early August, and entered September on a four-match winning streak with help from rookie striker Josh Wolff as a substitute.

[38] Chicago finished a two-game sweep of the series with a 1–0 victory at Mile High Stadium in Denver during the second leg, taking the lead with another Kubík penalty kick and several saves by Thornton to keep the shutout.

[39] The Fire then played against the Galaxy in the Western Conference Final, which began with a 1–0 Chicago victory at the Rose Bowl that was decided by a late header scored by Jesse Marsch off a free kick.

[40] The second leg was played in front of 32,744 fans at Chicago's Soldier Field, setting a new league playoff record, and resulted in another series sweep as the Fire advanced to the MLS Cup final.

[41] D.C. lost six members of their cup-winning roster in the 1997–98 offseason, including striker Raúl Díaz Arce and midfielder Ben Iroha to comply with salary cap limitations and three players picked by Miami in the expansion draft.

[51][52] Without Pope and Agoos, manager Bruce Arena used several lineups with reserve players and different formations, but the team ended their home winning streak in June by losing to the Dallas Burn in a shootout after a 4–4 draw.

[52] United remained atop the Eastern Conference, with only four points above second place,[54] and regained Agoos and Pope in July at the start of a nine-match winning streak that lasted two months.

[62] United faced the Miami Fusion in the Eastern Conference Semifinals but remained without Agoos, Pope, Etcheverry, and forward Tony Sanneh, who was injured in the regular season finale.

[63] Arena also swapped out starting goalkeeper and league shutout leader Scott Garlick for backup Tom Presthus, who had a stronger record in shootouts.

[64] D.C. won 2–1 at home in the first leg of the series with a pair of goals in the first half from Roy Lassiter and Jamie Moreno while successfully suppressing the Miami offense.

[68] United hosted the Crew in the first leg and won 2–0 with a pair of second-half goals from Sanneh and Etcheverry to complement a strong defensive performance that shut out league scoring leaders Stern John and Brian McBride.

[69] The second leg marked the end of D.C.'s 13-match playoff winning streak after the team lost 4–2 to the home side on the narrow pitch at Ohio Stadium in Columbus.

For the third consecutive year, the ABC broadcast was led by play-by-play announcer Phil Schoen and color commentator Ty Keough, who were joined by field reporters Seamus Malin and Bill McDermott.

[79] The Fire relied on stronger defending and counterattacks, including from recovered winger Roman Kosecki as a surprise starter, and had five more days to rest after clinching the Western Conference title.

A rebound shot by Tony Sanneh was blocked and fell to Marco Etcheverry, who tripped in the six-yard (5.5 m) box after a challenge by Luboš Kubík, but no penalty was called by referee Kevin Terry.

[83][84] Chicago's first scoring chance came in the sixth minute as Piotr Nowak delivered a low cross into the box that was deflected towards goal by Chris Armas, only to be cleared off the line by defender Jeff Agoos.

[80][88] United looked to quickly score an equalizer and earned set-piece chances, but the resulting headers from Roy Lassiter and Jaime Moreno went off target.

[86] After a run up the left wing, Nowak cut in towards the center of the penalty area and shot between several players, including Diego Gutiérrez, who deflected the ball into the goal.

[80] United protested the goal, arguing that the deflection had been off Gutiérrez's arm and Razov had been in an offside position while blocking the sight of Presthus, but Terry's decision was unchanged.

[88][91] Armas was assigned to tightly mark Marco Etcheverry, preventing him from creating plays for United and limiting the league MVP's involvement in attacks.

[88] Manager Bruce Arena congratulated Chicago on their performance but criticized the officiating of the match, including the no-call penalties and the offside positions during the second goal.