Victory would see Barca open up a three-point cushion at the Primera Division summit, with nearest challengers Atletico Madrid and Real Madrid not in action until Sunday.
And Martino, whose side advanced to the last four of the Copa del Rey in midweek with a 5-1 thrashing of Levante, acknowledged at his pre-match press conference on Friday that they could afford no slip-ups.
"When the season starts, you always talk about where teams will be in February," he said.
"Now we are in February and every mistake we make will be very expensive. We cannot neglect anything.
"The match against Valencia, and the semi-finals of the cup, mean it is an important fortnight, and then there is the Champions League after that. There is no margin for error."
Wing-back Dani Alves and midfield duo Sergio Busquets and Xavi returned to Martino's 18-man squad, but defenders Carles Puyol and Martin Montoya, fit-again midfielder Ibrahim Afellay and forward Isaac Cuenca were not involved.
On Puyol's absence, Martino reassured: "There's no problem. We just think that after his comeback the best thing now is not to play two games in a row."
Neymar on Friday resumed individual training for the first time since suffering an ankle injury two weeks ago but was not in the match-day squad and Martino has vowed not to rush the Brazil forward's comeback.
Asked whether the 21-year-old could be fit for the Champions League last-16 first leg against Manchester City on February 18, the Argentinian replied: "I respect the decisions of the doctors. There is no deadline. If he's fine, he plays. If not, he won't."
Valencia coach Juan Antonio Pizzi named youngsters Robert Ibanez and Cristian Portu in his 19-man group for the trip to Catalonia, with defender Victor Ruiz missing out as he recovers from an ankle injury.
Sergio Canales and Ever Banega were not included ahead of likely moves away from the Mestalla before the January transfer window closes on Friday night.
Pizzi's side travel to the Nou Camp boosted by the signing of former Barca midfielder Seydou Keita on loan from Chinese side Dalian Aerbin until the end of the season.
The 34-year-old Mali international completed his medical on Friday morning and will immediately join up with his new side.
Eduardo Vargas has joined on loan from Napoli, while Andres Guardado has been loaned to Bayer Leverkusen, and forwards Helder Postiga and Dorlan Pabon have also left until the end of the season, for Lazio and Sao Paulo respectively.
Los Che head into the weekend 10th in La Liga on 25 points - 11 adrift of the top six.