By halftime of the RailHawks’ Sunday afternoon friendly against the Mexican club Monterrey at WakeMed Soccer Park, it became evident that what happened this weekend is going to define Carolina’s season.

In the meaningless match against Monterrey, the RailHawks played the opening 45 minutes with passion and purpose, two characteristics that were embarrassingly absent in a very meaningful visit from Puerto Rico on Friday.

If the RailHawks had defeated the Islanders — and had everything else around the USL First Division held true over the weekend — they would be tied for fifth place today. Instead because of the 2-0 loss, they are in ninth place, one point out of the last playoff spot, three points from the bottom of the table.

With a strong effort Sunday after a lackluster showing Friday, this weekend will be the catalyst for either a second-half turnaround or the season’s ultimate demise.

Carolina coach Scott Schweitzer is counting on the former.

“For us to be able to bring it two days later, now we all have to say, if we play that good all the time in our league, we’re not talking about our 20 points,” Schweitzer said. “We’re talking about our 30, 34 points. We’re not giving away goals at the end. We’re not tying games, we’re winning. Let’s all be honest with ourselves, recommit to the season, recommit to the team and everything that’s right and let’s go do it on the field.”

The inconsistent effort has baffled everyone affiliated with the team. There’s no question this team has talent, but that talent is undercut by a lack of focus and unity.

“We’re good. We’re a good team. We just don’t believe in each other,” said midfielder Martin Nuñez. “We turn it on and turn it off whenever we want. All 11 have got to be hungry for 90 minutes. That’s been the problem. We came out harder [Sunday], I guess, because they’re a different team and they’re a well-known team. So we came more hungry [and] tried to get to the game.”

The RailHawks also seem to suffer from a crisis in confidence.

When they score first, they get overconfident, like they’ve already won the game. That helps explain why they are 4-0-4 when they score first this year. In three of those ties, they allowed the tying goal in the final 10 minutes.

When they allow the first goal, they go into a shell, like they’ve already lost. That helps explain why they have never come back and won after allowing the first goal. They are 0-5-3 this year on such occasions and 0-16-6 all time.

“I think we’re our biggest enemy,” said forward Dan Antoniuk. “If we can cut out our mistakes and somehow find that urgency … then we’ll be all right.”

It’s worth nothing that the RailHawks have also netted their share of late goals. They scored a game winner in the 87th minute (at Miami) and netted equalizers in the 87th (against Seattle) and 90th minutes (at Rochester).

The timing of the visit from Monterrey was perfect. The RailHawks are 1-5-4 in the league since starting the season 3-0-4. They needed an afternoon where nothing was on the line. Sunday gave them a chance to just play. And because it was an exhibition, there were unlimited subs and everyone got the chance to see the field. Only three of the roster’s 25 players did not dress Sunday. Twenty of the available 22 players saw time.

If the RailHawks are to turn things around, they will have to go on an unprecedented run. They have never won three games in a row in the league. If they’re going to make a charge up the table, anything less than three points from any contest is insufficient.

If playing dreadfully Friday wasn’t enough motivation for a turnaround, the RailHawks needn’t look any farther than the team that humbled them for additional inspiration. When Carolina went to Puerto Rico for the teams’ first meeting of the season on June 12, the Islanders were 1-3-3 and in last place. They’ve since won seven of nine and are three points behind Charleston for first.

Carolina has 13 games remaining, so it’s not quite time to panic. But the walls are starting to close in. If they don’t turn things around soon, their season that was so full of promise will be full of failure.

Sunday was the first step toward reasserting the former.

“We’ve just got to be professionals,” said captain Frankie Sanfilippo. “We’ve got to know every game, we all should be 100 percent. Every game should mean something to everybody. I think [Sunday], everybody looked at each other and said, every day we need to do this in practice and game in and game out.”