Red Bull's four-time world champion, who has won five times in seven years at the high-altitude Autodromo Hermanos Rodriguez, has cut Piastri's lead ahead of him, in third place, from 104 points to 40 since August with a scintillating burst of form.
Piastri still leads team-mate Norris by 14 points, but he has lost his metronomic consistency and, as McLaren appear to be floundering to match Red Bull for pace, he appears also, like Norris, to be weighed down by the pressure of the title battle.
After finishing on the podium in every race bar one since the season-opener in Australia, his last three results have been a retirement, fourth and fifth.
His qualifying form has deteriorated at a similar rate.
Norris has also struggled for consistency, but appeared in Texas last weekend to have regained some confidence and pace as he finished second behind Verstappen, who had started from pole and also won the sprint.
He remains, however, without a win since the Hungarian race in August.
"They are weighed down with this looming battle," said former Indycar driver and prominent analyst James Hinchcliffe, speaking on the F1 Nation podcast.
"Even Red Bull in 2024, started the season strong, but once McLaren caught up... you started seeing their pit stops falter a little bit...
"Pressure is an interesting thing. You always want to be the hunted because it means you've got the points lead, but passing is tough in F1 - on track and in a championship."
'With Max, it can happen'
With the experience of four title triumphs, Verstappen heads into the season's run-in knowing what to expect and enjoying himself.
"If it comes down to the last race and they are tight on points, maybe in that moment Max is the man to follow," said two-time world champion Fernando Alonso.
"The McLarens have enough car advantage to fight between them, but with Max it can happen as in 2021."
While Red Bull bid to snatch glory from McLaren in Mexico's thin air and the final races, Ferrari travel in hope of an unlikely repeat of their last victory, claimed by Carlos Sainz in Mexico a year ago.
His successor Lewis Hamilton has yet to claim a podium in 19 races while team-mate Charles Leclerc has had six, including third last Sunday when Hamilton was fourth.
Ferrari team boss Fred Vasseur praised Hamilton's strong performance throughout the weekend, suggesting the 40-year-old Briton was back to his best as he seeks a third win in Mexico's carnival atmosphere.
Given that and McLaren team boss Andrea Stella's admission that Mexico is not a venue that will favour his team, Piastri and Norris are likely to endure another nerve-shredding weekend that reduces their advantage as they seek a first title double for McLaren since 1998.
Mercedes, with George Russell in form and also capable of claiming an upset win, lead the fight for second in the lucrative constructors' title race by seven points from Ferrari with Red Bull third, three points further adrift.
An unpredictable and dramatic high-speed contest, at more than 2,200 metres above sea level, is in prospect.
