Jamaica’s Reggae Boyz head coach Steve McClaren cut a composed but firm figure following Monday night’s Concacaf Gold Cup setback against Guatemala, as he highlighted a concerning lapse in mentality as the root cause of their underwhelming first-half performance and eventual defeat.

Coming off a resounding 3-0 win over the same opponents in World Cup qualifying just days earlier, expectations were high that with the team's style of play taking shape, they could repeat the feat. But their bark did not match their bite at the Dignity Health Center. In fact, the Boyz looked a shadow of themselves in the opening half—timid, reactive, and too often second-best in the physical exchanges.

However, McClaren believes the signs were there from the outset.

"The difference was in mentality. I think ultimately that's always the thing that wins a game. We expected a reaction from Guatemala after the other night because we would do exactly the same, and that is what we said to our players. We knew they'd come at us; we knew they'd be aggressive. I thought the atmosphere was great, and I think they (Guatemala) deserve credit because with the crowd behind them, I think they fought like lions," McClaren said in a post-game press conference.

The Guatemalan crowd created a cauldron of hostility that McClaren said tested his team’s character, and though they weathered the early storm, a momentary lapse was punished in the 33rd minute.

Oscar Santis pounced on that defensive lapse to poke home what proved to be the decisive strike. After Darwin Lom cleverly backheeled a lofted ball into Santis’s path, the 26-year-old slotted past Andre Blake. It was a historic result for the 106th-ranked Central Americans, as it marked their first-ever victory over the 63rd-ranked Jamaicans in the competition and their first win against the Caribbean side in 13 years.

"They really had a big desire to win that game. When you're the underdog, which, obviously after the first result, Guatemala felt that, and they performed like underdogs. We got through the first 30 minutes, but we switched off just for a moment, didn't deal with quite a simple ball, and went a goal down, and it's always going to be difficult then. We did everything we possibly could. What we've got to do now is turn that around and make sure that we react on Friday and make sure that we prepare properly. And really the reaction is, we have to win on Friday," McClaren declared.

That all-important clash against Guadeloupe at PayPal Park in San Jose is now pivotal, as the Boyz need back-to-back wins to stay alive in the tournament. With Panama and Guatemala each sitting on three points, McClaren knows the margin for error is razor thin. As such, he pointed out that the emphasis heading into the next match will be on reigniting the aggression and hunger that defined their earlier success.

"People talk a lot about tactics and this formation, that formation, but at the end of the day it's about how we play. It's about being aggressive, winning jewels, and getting the basics right. We tried, but the first 20 minutes were so, so important. We've got to make that first 20 minutes ours in every game," the tactician noted.

Still, there were bright spots amid the disappointment. Chief among them was the return of striker Michail Antonio, who featured late in the second half after a long road back from a frightening accident.

"He trained with us two weeks ago in London. We said then it was a miracle. He's come on the field, and that's from where he was after the accident to be playing, to be walking; he's a miracle. So we're delighted. We need that kind of leadership, and so we'll build up his fitness as much as we possibly can. So it was good to get him minutes on the field," the former England boss shared.

But as one key piece returned, another was missed. Midfield anchor Isaac Hayden, sidelined with stomach cramps and respiratory issues, left a gaping hole in Jamaica’s structure, one McClaren admitted remains a tactical concern.

"That six has always been a problem. I know in the past we've had Damion [Lowe] in there, who you saw today (Monday). There was some aggression, and he is someone who could break up play, and he certainly did that on a few occasions. I think [Joel] Latibeaudiere came in and did well in the second half. So Isaac is a big loss, but we have to deal with that, and somebody has to step in and step forward, take the mantle, and help the team in that position," he ended.