The Union's last practice before Wednesday night's U.S. Open Cup semifinal against the Chicago Fire at Talen Energy Stadium ended differently than most practices do.

One by one, each player stepped up to the little white spot 12 yards from the goal line to practice penalty kicks. It's one of soccer's most famous traditions, and it returns to the spotlight any time a knockout-style tournament takes center stage.

"You want to avoid them at all costs," Union manager Jim Curtin said. "I'd prefer not to go into penalty kicks and take care of business in 90 minutes, knowing that we have New England on the weekend. But it's the reality of this competition, it's the reality of soccer."

Some teams don't think penalty kicks are a big deal. Others, most famously England's men's national team, obsess over them. The Three Lions' shootout win over Colombia at this summer's World Cup was their first ever in the tournament, and their first in any major tournament in 22 years.

But nearly everyone agrees on two things: it isn't the fairest way to settle the score, and it's much more of a mental test than a physical one.

"You can practice all you want, and a game situation is always going to be different," Union midfielder and captain Alejandro Bedoya said. "For me, it's just trying to get the proper technique down, and trying to get it exactly where you want to hit it in a game situation. … Sometimes you need a little bit of luck, too."

MLS had a decent idea in its early years: players had to dribble toward the goalkeeper and then shoot, with a running clock to keep things honest. But it was dismissed by the rest of the sport as an American gimmick. The Open Cup never used it. The league moved to the traditional format in 2000.

The Union have known joy and heartbreak in Open Cup shootouts. They won one in 2014 and two in 2015, and were knocked out of the tournament that way in each of the last three seasons — including the 2015 final in Chester. They also lost a 2011 qualifying playoff in a shootout.

If it comes to penalties again on Wednesday, Curtin and his players will be ready. Along with Tuesday's practice run, Curtin and the squad already know who the required first five takers will be. He also knows how good goalkeeper Andre Blake is in net. Perhaps that will be enough to earn a better fate from the soccer gods this time.

Union vs. Chicago Fire

U.S. Open Cup semifinal, Wednesday, 7 p.m. at Talen Energy Stadium

Live streaming: Available at ussoccer.com. There is no TV broadcast.

How the Union got here: Beat the USL's Richmond Kickers at home in the fourth round; beat the New York Red Bulls at home in the round of 16, beat Orlando City at home in the quarterfinals.

How the Fire got here: Beat the Columbus Crew on the road in the fourth round; beat Atlanta United on the road in the round of 16; beat the USL's Louisville City at home in the quarterfinals.

Chicago players to watch

GK Stefan Cleveland: The 24-year-old Ohio native — Dayton, though, not the town in his name — made his pro debut this past Saturday, and had eight saves in a 2-1 loss. Will he get the call again on Wednesday?

M Aleksandar Katai: His nine goals and four assists make for the highest combined total on the team.

F Nemanja Nikolic: Every time the Union play the Fire, he's featured here. He'll keep being featured as long as he keeps scoring, because that's why you spend big money on a striker.