MLS Playoffs: The good and the bad from the second day of Knockout Round games

Home-field advantage is indisputably a thing in Major League Soccer.

During the regular season, 19 of 20 teams played to a winning record at home – only the feckless Houston Dynamo failed to do it, and they posted a 5-5 ledger in games that didn’t end in a tie. On the road, meanwhile, not a single team had a winning record.

Blame the travel. Blame the disparate climates. Blame the varying altitudes. Whatever.

Now consider that in the one-off Knockout Round games going back to their inception in 2011, the home team had a 12-2 all-time record going into Thursday. And for four years and 11 straight games, the home team had won every single game.

Which is what made it so disheveling to see D.C. United, which had been on a good run (undefeated for six in a row until the final game of the regular season, winning four of those) and seemed primed for a playoff push, go down 4-0 to the Montreal Impact on Thursday. At home.

Especially considering Montreal sort of stumbled to the finish line. Manager Mauro Biello apparently had a falling out with his superstar Didier Drogba, who may or may not have actually been injured and perhaps or perhaps didn’t refuse to take the field – or the bench. Nobody had ever lost a Knockout Round game at home by more than two goals. D.C. United wouldn’t either, although it took 89th- and 93rd-minute goals to salvage a slightly more palatable 4-2 loss.

Predictably, the Impact defended soundly and broke out through star playmaker Ignacio Piatti. And just four minutes in, Laurent Ciman put the Canadians ahead off a corner, when he was given far too much space.

The Impact retained the edge in what for much of the first half was a tight game. Although Luciano Acosta had a somewhat credible penalty claim for United.

But then Piatti, with a little room, curled in a ball into the recently arrived and sensational Matteo Mancosu, who finished surgically before halftime.

Before the hour, Piatti uncharacteristically misplayed a ball, but it skipped on to Ambroise Oyongo, who swung a cross at Mancosu for a header that beat goalkeeper Bill Hamid and give the Italian his second goal.

United might have gotten into the game at that point, but Rob Vincent missed an open goal.

It was that kind of day for D.C. for the bulk of the game. It took until the 76th minute for the home team to even get a shot on goal, which was cleared off the line by Dominic Oduro. A while later, Hernan Bernardello cleared a ball off the Impact’s line with a header as well.

But then Piatti and Mancosu put the game away. They pinged the ball back and forth on a counter until Piatti finally finished it off.

After Hassoun Camara had to come off late on for the Impact with a head injury with no subs remaining, United finally gave a spasm of life. In the 89th minute, Patrick Nyarko swung in a cross to Lamar Neagle, who headed in a consolation goal.

Then, deep in injury time, Taylor Kemp skipped around Ciman’s tackle far from goal and dispatched a laser that kissed the inside of the near post and went in.

But it was much too little and far too late. In perhaps its worst showing of the year, United frittered away not just its precious home-field advantage but also its entire season.

SOUNDERS EKE OUT WIN OVER SPORTING K.C.

Was it deserved?

Probably not.

Was it fair?

Nope.

Was the Seattle Sounders’ lone goal offside?

Most definitely.

But that wasn’t held against Nelson Valdez, the Paraguayan who had been such a high-profile signing for the Sounders last year but struggled hugely to score goals. His 88th-minute goal saw the Sounders through in a tight, testy and chippy 1-0 home win over Sporting Kansas City (making the home teams 13-3 in the Knockout Round all time).

In truth, Sporting was probably the better team with the better chances and a high press that unsettled the Sounders from the first whistle. It was sort of miraculous that the Sounders were in the playoffs at all, after their dumpster fire of a regular season in which they ended strong to qualify anyway.

That SKC pressure gave the visitors a series of chances in the first half, forcing good saves from Stefan Frei. Paulo Nagamura ripped a shot on a bad turnover, parried by Frei.

Graham Zusi then hit the post the one time Frei was beaten.

As the game grew increasingly physical and contentious, SKC kept the upper hand. This time around, Roger Espinoza forced the intervention from Frei.

Early in the second half, Sporting seemed to have gone ahead. But when Matt Besler headed in a free kick, he was adjudged to have been offside by inches – it probably didn’t help that he started in an offside position, waiting for the rest of the pack to catch up.

Left back Seth Sinovic even got in on the action, challenging Frei.

Things got acrimonious when Sporting’s Benny Feilhaber was seemingly chopped down by Osvaldo Alonso, who was already on a yellow. The Cuban somehow avoided a second even though the tackle looked bad, while the contact was light.

Feilhaber lost his cool.

And then the one-time United States national teamer responded with a long, mazy run that almost won it for his team.

But then Seattle finally began forging chances. In the 83rd minute, Roman Torres met a ball at the far post but somehow managed to bundle it wide.

And, at length, Valdez won it. Joevin Jones beat Zusi and whipped in a cross for Valdez. He was a tad offside, certainly more so than Besler had been, but scored on the diving header and it was allowed to stand.

Sporting was the superior team, but whereas its offside goal was disallowed, Seattle’s was counted. And, fairly or not – the correct answer is not – the Sounders move on to face the Supporters’ Shield winners – FC Dallas – in the Conference Semifinals for a third straight year.

Leander Schaerlaeckens is a soccer columnist for Yahoo Sports. Follow him on Twitter @LeanderAlphabet.