Sometimes, even the lightest of opponents can still be taken too lightly. Mexico assumed that it had nothing to fear from New Zealand, which had lost its Confederations Cup opener to a fairly fetid Russia 2-0. So El Tri and its head coach Juan Carlos Osorio figured they could cruise to three points and rest the regulars at the same time on Wednesday.

Wrong.

The All Whites, clad in all black, gave the Mexicans — playing with an almost entirely new lineup from Sunday’s 2-2 draw with Portugal — a scare with a strong first half that produced a lead at the break through Chris Wood. But tallies by Raul Jimenez and Oribe Peralta salvaged a 2-1 win for El Tri, all but seeing them through to the semifinals. A tie with Russia in their final game will do the job.

But it was a nerve-wracking ordeal for El Tri, who turned in perhaps their worst half in memory before a much sharper second act turned things around. New Zealand is a completely unremarkable national team — ranked 95th in the world by FIFA and 62nd by ELO — and is only in this tournament because it dominates its Oceania confederation of tiny and unathletic island nations. They are the proverbial one-eyed kings in the land of the blind.

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Yet the way things were going, Mexico could have suffered its first loss in a competitive game since the quarterfinal of last year’s Copa America Centenario.

Because the first half was utterly feckless for Osorio’s second string. All his side really produced was a limp header by Gio Dos Santos after Javier Aquino’s run up the left. But Dos Santos got mixed up with his fellow forward Peralta and nodded the ball off him, before it trickled wide.

Osorio lost his mind on the sideline when Carlos Salcedo was whacked down by Wood on a run where the defender instigated the first contact. With Salcedo still down, and soon to be stretchered off with his head immobilized, Wood got the ball back but was denied well by Alfredo Talavera.

In the 42nd minute, Wood would convert his second fat chance. Nestor Araujo made an incomprehensibly bad clearance, which was played on to Wood. He was kept onside and scored cleanly:

Wood got yet another look before the halftime whistle but failed to deal Mexico a further blow. And with that small grace, El Tri would turn it around. Mexico was more dangerous in the first few minutes after the break than the entire first half combined. It helped that Hector Herrera had entered the fray during the break to improve the non-existent ball distribution.

Before Mexico would score, Wood had yet another opportunity. He was denied one-on-one by Talavera. Then, in the 54th minute, Aquino carved open some room up the left and began an attack that teed up Jimenez, who turned and fired. His shot was deflected slightly but stayed on a true course into the net:

Aquino again created a goal in the 72nd minute, when he turned the corner on his defender and cut back for Peralta, who whacked it in off the near post.

The sides exchanged a series of good chances before the final whistle, highlighted by Ryan Thomas’s smashed curler off the upright. But the game ended in ugly scenes as a giant brawl broke out in injury time. Extensive consultation with the video assistant referee yielded a few yellow cards but wound up breaking the rhythm of the game, suggesting again that the protocol for using the technology needs much tweaking.

Mexico saw out the win though and collected the points. And breathed a sigh of relief.

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

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