The U.S. Open Cup finalist won 2-0 at Western Conference-leading LAFC three weeks ago and delivered a needed 3-1 home victory over Real Salt Lake last weekend. It also has lost at slumping Houston, Sporting Kansas City and Colorado, among others, and tied Vancouver and Orlando City at home.

Is the disparity simply a team newly assembled this season learning to play together?

"No, that's a team not being prepared to play on the night," United coach Adrian Heath said. "This group can play. We know that."

United has played well enough despite lost opportunities to clinch its first playoff spot on Sunday with a victory at Portland, thanks to Atlanta's victory over San Jose on Saturday.

Player absences and changing lineups and formations might have contributed to those lost opportunities. But Heath notes that even Tottenham Hotspur coach Mauricio Pochettino in England's Premier League wonders why a team that finished runner-up in last season's UEFA Champions League is winless in its past nine league road games.

"I don't know, Pochettino doesn't know," Heath said. "You don't know sometimes. You think you know what the reasoning is, but we're human beings. The players are human beings. You have games when it's good. You have games when it's not so good."

By adding five starters over the winter and another three players during a summer transfer window, United has improved enough to have not only a playoff spot in sight but one with home-field advantage. Starting with a match at Portland on Sunday, it has four regular-season games left.

The team has not improved enough to consistently deliver results like its inspired victory at LAFC. Its next time out in MLS play, United lost at Houston, which was 0-6-1 in its previous seven games.

"It's pretty easy to get up for a place like LAFC because of the atmosphere and what was at stake," United veteran midfielder Ethan Finlay said. "We were feeling it, we had a game plan and we executed it really well. Houston was one of those 'trap' games where you look at it on paper and we should have gone in there and you probably marked us down as a win or a draw at least.

"You can't do that in this league, regardless of where you are in the season. We just came out flat and there's no rhyme or reason. There's no excuse."

Heath blistered his players during a halftime speech at Houston after his team trailed 2-0. He credited them for better play in that second half, and in Sunday's important victory over Real Salt Lake.

"This is a really honest group," Heath said. "I know if we get after them, invariably we get a response. The disappointment is I have to go through that at halftime to get a response. But the group responded to it. They do respond."

After Sunday's match, United plays at home Wednesday against Sporting Kansas City and next Sunday against LAFC before finishing the regular season on Oct. 6 at Seattle.

"We've got a huge four games coming up," Heath said. "When you start off as a small kid, this is the time of year you want to play for. Everything is on the line. We're at stage of the season where every game has an implication either for yourself or somebody else."

Portland is nearing the end of a 10-game homestand — 11 of its final 12 are at home — after it started the season with 12 consecutive road games while its Providence Park stadium was renovated. Yet the Timbers remain in eighth place, one point from a playoff spot after losses in four of their past six home games preceded by home draws with Colorado and Orlando City.

"People always talk about home games," Heath said. "Home games are always difficult when you know you have to win. That's what Portland is going through now. The pressure starts to mount and it's not easy. We've got to go there. The games against them at Providence Park have been closer than the score line suggested. I know if we play well, we can go there and compete."