La Liga Preview: Barcelona v Osasuna
The Catalan club's prospects of retaining the La Liga crown have been significantly damaged after a number of surprising defeats in recent weeks.
Martino's men were stunned 1-0 by struggling Real Valladolid last weekend, slumping to a loss against a side that is battling against relegation and had won just four previous league matches this campaign.
That setback made it three defeats in six league games for Barca, with the other two reverses coming against Valencia and Real Sociedad respectively.
Barca are third in La Liga as a result of their poor form, four points adrift of league leaders and arch rivals Real Madrid.
Valladolid's shock victory over the 22-time Spanish champions has led to scathing criticism of Martino, whose position has come under increasing scrutiny.
However, the Argentinian was able to silence his critics somewhat in midweek with a 2-1 (4-1 agg) success against Premier League side Manchester City in the UEFA Champions League last 16.
And Barca will be confident of building on that triumph against an Osasuna side that has lost on all of their last five visits to the Camp Nou in all competitions, conceding 21 goals.
Osasuna did hold Barca to a 0-0 draw in the reverse fixture in October, but two consecutive defeats have seen them pulled back into the battle against relegation.
Javi Garcia's side are only three points clear of safety heading into the weekend's fixtures, with 11 games remaining, and could be pulled even further towards the drop with defeat at Barcelona.
However, despite Osasuna's current struggles, striker Oriol Riera, who spent six years as a youngster at Barcelona, is hopeful they can prove to be a test for their hosts.
"Playing against one of the top three sides is always very difficult, but we're going there keen to make things difficult for them," he told the club's official website.
"We will make their lives difficult. At least, that's what we’ll be trying to do."
Jonathan dos Santos (knee) and Isaac Cuenca (hamstring) are both out for Barcelona, and Martino may elect not to play defender Gerard Pique, who is on the verge of a suspension.
Pique is one booking away from a ban and will miss next weekend's Clasico clash with Real should he receive a yellow card on Sunday.
Meanwhile, Osasuna could welcome back defender Marc Bertran (hamstring), while Sisi (knee) and Miguel de las Cuevas (toe) are still on the sidelines.