Parejo was handed a rare start in the 4-2 win over PSV Eindhoven on Thursday night and on a personal level is hoping his performance against the Dutch side can kickstart his Valencia career after a difficult first season.
He told AS, "I am happy with the result and also with the way I played and worked.
"Sometimes, even when you lose, if you have given your all you have to be satisfied. My time here didn't start well but now I am very happy.
"There are three very important points to win on Sunday. The (1-0) victory in Granada (last time out) was positive, but to be a good side we need to win at home, we need to play a good game to regain our confidence.
"The league is what allows you to play in these great European competitions."
Coach Unai Emery is expected to make a number of changes to the side that beat PSV with the likes of Jordi Alba, Sofiane Feghouli and Tino Costa likely to start.
Mallorca goalkeeper Dudu Aouate though does not believe Valencia's European exertions will have too much of an impact on the game.
He told the club's website, "Valencia have an ample squad and a top manager so I don't think they will be tired after the Europa League, we can't depend on that.
"Emery knows how to rotate his squad well and they are a very strong team physically.
"We're perfectly aware that we are now entering an important stage of the season, we are playing against a great team, but we have to continue with what we do well. Playing as a unit and defending well we will have a chance to take a positive result."