Having kept six clean sheets in eight matches heading into this clash, the notoriously stable Argentina defence was given its fair share of tests in a tricky opening period in Texas.
Moises Caicedo and Jeremy Sarmiento both found themselves denied by Emiliano Martinez in the early going, while Kendry Paez fired over as Ecuador started on the front foot.
However, Lionel Scaloni’s men soon gained a foothold and started to threaten an opener, with Enzo Fernandez spearheading the charge, heading narrowly wide before having a promising effort deflected off target.
The pressure would soon tell on La Tricolor though, with the reigning champions making the breakthrough 10 minutes before the break.
Lionel Messi’s corner was brilliantly flicked on at the near post by Alexis Mac Allister, leaving the arriving Lisandro Martinez with a simple task to head home his first international goal and hand Argentina a half-time lead.
Ecuador were in need of a response, and after a quiet opening quarter-hour of the second period, they looked set to provide one as they were awarded a penalty for handball against Rodrigo De Paul.
Enner Valencia assumed responsibility from 12 yards, but despite having sent penalty-saving specialist Martinez the wrong way, the Ecuador captain saw his spot-kick come back off the post.
With the contest still on a knife edge heading into the closing stages, the big-game experience of the Argentina players came to the fore as they smartly managed the contest, disrupting the flow and frustrating the Ecuadorians.
That was until the 91st minute, when Scaloni’s men finally conceded for the first time at this year’s Copa when Kevin Rodriguez headed home John Yeboah's cross to snatch a dramatic equaliser and send the contest to a penalty shootout.
The pressure was now on the world champions, and it showed immediately as captain and talisman Messi failed with an audacious panenka and saw his effort come back off the bar.
Martinez immediately got Argentina back on track by saving Angel Mena’s effort, and repeated the act to deny Alan Minda from the very next spot-kick.
That set the wheels in motion for another famous Argentinian shootout triumph, with Nicolas Otamendi converting decisively from 12 yards to send Scaloni’s men into the semi-finals of a fifth successive Copa.
Flashscore Man of the Match: Lisandro Martinez (Argentina)
