The Spain international, who has scored 33 goals in all competitions this season, will miss the game at the Vicente Calderon with a hamstring problem picked up in midweek
The Spain international, who has 33 goals in all competitions this term, is set to sit out the game at the Vicente Calderon after picking up a hamstring injury in Tuesday's 1-1 draw at Barcelona in the Champions League quarter-final first-leg.
The club confirmed on Wednesday that the forward had suffered a grade one hamstring strain, but there was positive news in that the muscle was not torn.
Even so, the injury is a significant blow for the hosts and looks likely to rule the 25-year-old out of this weekend's game, with experienced front man David Villa expected to take on the burden of Atletico's goal-scoring responsibility as they look to avoid any slip-ups in their Liga title charge.
Diego Simeone's men have been the surprise package of 2013-14, defying expectations to sit top of the table with just seven games remaining.
Atleti's performances have provided a serious threat to the Barcelona-Real Madrid duopoly that has dominated the Spanish game for the past 10 years.
Since Valencia won the title in 2004, only Atletico's opponents on Saturday, Villarreal, have broken into the top two, with a second-placed finish behind Madrid in 2008.
The 1995-96 champions have kept pace with the leading pair throughout the campaign, though, and, after a slight blip where they won just three out of eight league games between January 11 and March 2, Simeone's side seem to have found their form once more, winning their last five La Liga outings without conceding a single goal.
That defensive solidity has been a constant theme throughout the campaign, with their goals-against tally of 22 the best in the league.
Simeone, who was a player with the club when Atleti last won the title, has also steered his side to the last eight of the Champions League for the first time since 1996-97.
But their attention now turns to a match against a side who have European ambitions of their own, with Villarreal just one point away from a Europa League qualification spot, and just seven shy of fourth-placed Athletic Bilbao.
Marcelino's charges have suffered something of a loss of form in recent weeks, winning only one of their previous six league games, and have lost four of their last six on the road.
The visitors would be happy with a repeat of the reverse fixture in November, when Ikechukwu Uche's equaliser cancelled out Mario's early own goal in a 1-1 draw.
They face a daunting challenge however, as Atletico remain unbeaten at the Calderon this season with only Barca, Real and Sevilla claiming draws from their 16 matches at home.