Messi has been struggling with a thigh injury and missed the last two Primera Division games although Barca have continued to shine in his absence, with a 5-0 win over Real Mallorca followed by a 3-0 triumph against Real Zaragoza.
And, despite returning to training on Thursday, it is expected the Argentinian will be rested for Saturday's clash at the Nou Camp as Barca prepare for their Champions League semi-final encounter with Bayern Munich three days later.
Not that Martinez is expecting Messi's absence to make the task any easier against a side who go into the weekend 13 points clear at the top of the league.
He said: "He may not be playing but he has not played in the last two games and I think they have an 8-0 aggregate.
"We must be bold when we have chance, but we have to be very strong defensively.
"Both Real Madrid and Barcelona are games that you know are going to be difficult. Their statistics are ridiculous, so it's another nice challenge for Saturday."
Just as Barca are 13 points clear at the top of the league, Levante are 13 points away from the relegation zone and virtually assured of top-flight football next season.
Second-placed Real Madrid host Real Betis on Saturday as they attempt to keep ahead of city rivals Atletico, who travel to Sevilla on Sunday.
Just three points separate the two sides who will meet in the Copa del Rey final on May 17 and Atletico winger Juanfran wants to finish the season with a flourish.
"For us it is a very exciting final course," he said. "We have some big games in which everything will be decided and we will see if our season has been good, very good or great.
"We want to finish second and win the cup final, but first we have a match against Sevilla.
"Encounters at the Sanchez Pizjuan are always very hard."
Relegation-threatened Mallorca take on Rayo Vallecano on Friday night and will be desperate for a win to take them out of the relegation zone and apply some pressure on the teams around them.
The other two teams in the drop zone play on Monday night as Celta Vigo host Zaragoza.
Malaga travel to Valencia on Saturday with both sides level on 50 points and three points for either would move them to within a point of fourth-placed Real Sociedad who travel to Osasuna on Sunday.
Granada host Real Valladolid on Saturday while in Sunday's remaining games Getafe take on Espanyol and Athletic Bilbao travel to Deportivo la Coruna.