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The Fire are the league's hottest team, mostly because of their offense. But Sporting KC has been cooling off plenty of opponents with the league's best defense.
No team has seemingly snuck on MLS quite like the Chicago Fire have this year.
Sure, expectations were pretty low at the start of the year for the San Jose Earthquakes, but they've played so well that even their biggest detractors have been grudgingly recognizing their quality for several months.
It could be argued that the Columbus Crew were considered almost laughably bad at one point, but they've now cooled off anyway.
The Fire are another beast all together, as they started kinda slow, picked up steam and are now in position to take over the lead in the Eastern Conference if they can beat Sporting Kansas City on Friday.
Along the way, they've managed to create numerous opportunities for doubt yet manage to come through it each time. Let's remember that this team started the season with a very mediocre 5-5-3 record and didn't win consecutive games until winning three straight right around the midway point of the season.
Many of their higher-profile offseason acquisitions proved to be total busts, illustrated by the fact that Frederico Puppo and Rafael Robayo are no longer with the team.
Just as the team seemed to be coming out of their doldrums, they found out that midfield maestro Sabastian Grazzini was going to be leaving them. About a month later, Marco Pappa left the team. The relative importance of both players can certainly be debated, but their productivity did not seem easily replaced.
High-profile moves like this surely have contributed to the lack of faith in what the Fire were and have been doing.
The reality, though, is that the Fire have simply been an elite team for about two months now and pose a very real threat to Sporting KC, a team who seemed to be running away with the Eastern Conference crown about two months into the season.
The Fire come into this game having won four straight and having gone 7-1-1 over their past nine. Only the LA Galaxy can match that recent run of excellence. Chris Rolfe, who joined the team at midseason, has scored seven goals during that stretch.
It is worth noting that the Fire have done this mainly by beating teams they should be. One one of those seven wins has come against a team currently in playoff position. Against the two best teams they played during that stretch -- the Earthquakes and D.C. United -- they tied and lost, respectively.
Their big test, then, comes on Friday.
Sporting KC may not have as flashy of a recent run, but they do come into this game riding an eight-game unbeaten streak (5-0-3), albeit with only two of those wins coming against teams in playoff position.
While the Fire have been fueled by an offense that is poring in 2.22 goals per game during their nine-match run, Sporting KC has done it with defense. They've given up just four goals in their past eight matches and picked up four shutouts, giving them a league-best 13 clean sheets for the season.
That's basically how Sporting KC has done it all year. They currently lead MLS with 25 goals allowed, which is six fewer than any other team. At Livestrong Sporting Park, it's almost impossible to score against them, as they have allowed just 11 goals in 15 matches.
The Fire, impressively, have actually managed to do that enough to win each of their previous encounters. But this is the first time they've met with stakes as obvious as these. Nothing less than the top seed in the East is on the line.