The victory, with Fabregas netting a hat-trick and Alexis scoring twice, restored Barca's 13-point advantage over Real Madrid at the top after their arch rivals had thumped Levante 5-1 in the earlier kick-off.
It was a timely confidence boost for Barca ahead of Wednesday's Champions League quarter-final, second leg against Paris Saint-Germain and included the emotional return of defender Eric Abidal a year after he underwent a liver transplant.
It is still not clear if Messi, who damaged a hamstring in last week's 2-2 first-leg draw in Paris, will be available to face PSG.
On Saturday's evidence Barca would manage without him as Fabregas and Alexis combined superbly to see off Mallorca, who will end the weekend at the bottom of the table.
Coach Jose Mourinho left a number of key players out of his starting line-up as Real prepare to defend a 3-0 lead at Galatasaray in Tuesday's Champions League quarter-final, second leg.
Kaka put Real ahead from the penalty spot in the 38th minute after Christian Lell's handball and Ronaldo volleyed into the net from close range and set up Ozil for Real's fourth after coming on in place of Jose Callejon at half-time.
Ozil stroked in Real's fifth in added time as the champions moved on to 65 points from 30 matches.
"The players who do not get many chances have these matches to prove they are capable of being in the side," assistant coach Aitor Karanka told a news conference.
"We are also motivated by finishing second, because Atletico are close behind and we have to keep going so they can't go ahead of us," he added.
