scored the only goal as Minnesota United sent St. Louis City crashing to their first defeat of the season in Major League Soccer on Saturday.
Amarilla stepped up to rifle home a 78th-minute penalty at CityPark to ensure that the visiting Loons maintained their own unbeaten start to the campaign.
Amarilla, a Paraguay international, had won the spot-kick moments earlier after darting into the penalty area and being brought down by a clumsy challenge from St. Louis's Canadian international Kyle Hiebert
The defeat is the first blemish on expansion club St. Louis' impressive start to its debut MLS season. Prior to Saturday, St. Louis had a 100 percent record, with five wins out of five to lead the Western Conference by five points.
"We knew we'd have to ride our luck a little bit at times and we did that on occasion in the first half," Minnesota head coach Adrian Heath
said after his team's win. "I thought we did that, and in the second half we were outstanding and far and away the better team," the former Everton forward said. "Without the energy levels, and determination and enthusiasm to run around and defend the goal, none of this is possible."
Minnesota is fourth in the Western Conference standings, with 11 points from five matches.
Although St. Louis remains on top of the standings after Saturday's loss, the lead has now been trimmed to two points after the Seattle Sounders grabbed a 2-1 away victory over the LA Galaxy.
The Galaxy — the most successful team in MLS history, with five championships in nine MLS Cup final appearances — is still awaiting its first win of the season and is languishing in 12th place in the 14-team Western Conference.
Galaxy fans have staged a series of protests calling for the dismissal of club president Chris Klein
during the opening weeks of the season, and boos rang out on Saturday after Brazilian winger Leo Chu
's low strike fired Seattle into a 2-0 lead after 35 minutes.
U.S. international Jordan Morris
had given Seattle an early lead after 21 minutes, tucking away a low finish from close range after a sweeping counterattack sliced apart the Galaxy back four. Jalen Neal
pulled a goal back for Galaxy on 63 minutes, but Seattle held on to claim all three points. In the Eastern Conference
, FC Cincinnati has a one-point lead at the top of the standings after a 1-0 win over Inter Miami. FC Cincinnati is unbeaten after six games and a point clear of Atlanta United.
Atlanta, thumped 6-1 by Columbus last week, bounced back from that loss with a 1-0 win over the visiting New York Red Bulls.
Atlanta welcomed back Argentina World Cup-winner Thiago Almada
following the international window, and the South American had a hand in the game's only goal.
Almada's rasping long-range strike was fumbled by New York goalkeeper Carlos Coronel
and Giorgos Giakoumakis
was on hand to stab home the rebound. rcw/smw
© Agence France-Presse
This by far was the worst loss ever in the history of the franchise.