The Blancos are 13 points behind Barcelona with 11 games to go, and the Portuguese centre-back is adamant the players remain motivated in matches such as Sunday night's.
He told reporters after the win: "We worked hard to get the three points. The most important thing is that the team has fought and put the effort in.
“Celta’s quality surprised me, because of their position [in the table], but they have a lot of quality, and I hope they get out of that [relegation battle].
“We were very focused on what we had to do and, though it's hard to fight in La Liga, any player who wears the shirt of Madrid must always be motivated to play for the club.”
Raphael Varane has recently displaced Pepe from the first team at Santiago Bernabeu, but Pepe insists there are no hard feelings between them and praised the French defender’s progress.
“I'm happy for Varane because he deserves it,” he added. “He has worked hard and is a player who has a bright future. Madrid are the only ones that can compare who is more favourable than the other.
“We have had a very turbulent season, but the most important thing is that we never drop our effort."
Following their progress to the Champions League quarter-finals in midweek after a 2-1 victory at Manchester United, Marcelo believes Madrid showed their battling side once again in domestic action.
The Brazilian said: "Today, I thank God that we have achieved the victory as that is so important. It was on a tough pitch, and Celta’s fans support their team strongly.
“We fought, struggled and the team were all very good. I feel good, I can improve but I feel fine.
“When people speak well of me it does not go to my head, and when they speak badly, criticism does not affect me.”