Novak Djokovic's shock exit at Roland Garros opened up the tournament bracket, although there will be a wait to see who out of Rafael Nadal and Diego Schwartzman will move into the semi final after their match was postponed until 12.00PM CET on Thursday.
The victor of the match will play either third seed Marin Cilic or Schwartzman's compatriot Juan Martin del Potro.
The Spanish No. 1 required treatment at the change of ends for a right wrist problems and at the start of the second, Schwartzman struck again.
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After roaring to a two-set lead, Nadal faced a stern test in the third with Marterer leading 3-1 at one point after breaking the Spaniard.
Three consecutive breaks - two for Schwartzman - gave the 25-year-old underdog the advantage in the second set before the first rain break.
He may have halted the mutiny for now but Nadal was strangely off-colour, unable to dictate the rallies as he usually does on clay.
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Nadal came into the match undefeated against the diminutive Argentine from their five previous meetings and was yet to lose a set en route to the last eight stage, while Schwartzman recorded a comeback five-set victory against Kevin Anderson in the fourth round.
Nadal, in the hunt for an 11th French Open title, trails 11th seed Schwartzman 6-4, 3-5.
More important than that, of course, is the match's ultimate outcome, and a significant moment came with Schwartzman serving while up 3-2 in the second after the initial delay. Nadal was nowhere near his best tennis, having to play against four break points in the very first game and suffering three breaks of serve.
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Nadal hit a floater that was possibly headed wide, yet Schwartzman attempted a volley that missed.