Marcelo insisted there are never any easy games for Real Madrid after the LaLiga leaders completed their comeback in the 90th minute.
Madrid survived an almighty scare in their 3-2 victory at Sporting on Saturday, overturning a 2-1 deficit as Isco struck the winner with eight seconds of regulation time remaining.
Isco's superb solo goal in the 1th minute was sandwiched in between Duje Cop and Mikel Vesga, who struck to give hosts Sporting the lead five minutes into the second half until Alvaro Morata and Isco turned the match on its head in the absence of Cristiano Ronaldo and Gareth Bale.
The win kept Madrid three points clear atop the table heading into Easter and a relieved Marcelo told reporters: "There is never an easy game.
"We've given every last bit in a difficult game. We didn't have much time to rest, those that have come in have been phenomenal and that is what makes the team great. When we need everyone, they're there.
"It is difficult, there isn't time to rest, but we are working very well and we're good physically. But, in the end, we have played a lot of difficult games."
Marcelo singled out Isco for praise following his game-winning brace on the weekend.
Constantly linked with a move away from the Santiago Bernabeu, Isco was recalled to the starting XI after the midweek Champions League win at Bayern Munich and netted a superlative solo stunner in the first half.
The Spaniard then broke the deadlock at the death with a strike from the edge of the penalty area.
"[Isco] has been very good, he is very happy with his goals but more for the result for the team," said Marcelo. "Isco deserves it, like everyone else he has been working.
"It is a relief to be able to score and take the three points, that was what we wanted.
"Before the game, we were thinking only about Sporting, but now it changes to Bayern, and later El Clasico. We are playing game-to-game."