Monreal has missed the last two months with a persistent back injury and although Los Boquerones have since qualified for the last 16 of the Champions League in style, they have struggled on the domestic front with just one win in their last six league games.
Pellegrini told the club's website: "It is important news. Monreal is a player that got injured when we were in a great moment.
"The team felt his absence but he has now recovered and we hope he will reappear at the same level.
"Granada is a distinct team because they have a distinct manager working for them. Their situation is perhaps worse than last season, but that just means we are going to face a team that will come looking for a result with a lot of intensity and with the need to get something within them.
"Therefore, as always, they will be a very difficult opponent."
There was also some bad news for Pellegrini on the injury front as Jeremy Toulalan has been ruled out for over a month with a hamstring tear, so Manuel Iturra should retain his place after coming in for the Champions League game against Anderlecht in midweek.
Granada are in even greater need of the points as they sit in the bottom three, but Dani Benitez believes the speculation surrounding manager Juan Antonio Anquela's job is unfair.
Benitez told Marca: "In this league any team can beat any other and we are capable of beating anyone, as we have already shown.
"The manager works at 100% and has already shown he knows how to solve some problems we had very well. In the games when we haven't won it is due to us, it is not the fault of the manager."
Benitez also insisted he would not be affected by being refereed by Clos Gomez for the first time since he was banned for three months for throwing a water bottle at the official towards the end of last season.
"With the suspension and having to watch from the stand, I have matured," he added. "There is nothing special, the moment has passed and I have spoken with him and apologised.
"I had to serve three months suspension and it's now done, he will be just another referee."