Mauricio Pochettino is prioritising Ligue 1 over other competitions in his first season at Paris Saint-Germain and is backing Sergio Rico after a difficult showing in the defeat to Lorient.

PSG were beaten 3-2 at Stade du Moustoir on Sunday, as the Parisians suffered their first loss under new head coach Pochettino.

Spanish goalkeeper Rico deputised for Keylor Navas between the posts, with PSG's first choice missing due to a stomach injury.

But Rico received widespread criticism for his performance, raising further doubts regarding his suitability as Navas' understudy and highlighting the Costa Rican's importance.

Navas looks set to miss Wednesday's visit of Nimes as well due to a groin complaint, meaning Rico is likely to keep his place in the team.

Since the start of last season, PSG have boasted a far better win percentage with Navas in the team (78.4 per cent of 37 games) than when Rico has started (57.1 per cent of seven matches).

They also concede twice as often on average when Rico is in the starting XI (1.4 goals per game) compared to Navas (0.7 goals per game), but Pochettino was keen to offer his backing to the 27-year-old.

"It is important that all the players are available so that the competition between them helps them to reach their best level," Pochettino told reporters on Tuesday.

"We have such a team that those who play less often have to be able to play and perform well when they are on the pitch.

"It is sometimes difficult to find positive elements when you lose a game, but we are happy with Sergio and his level in the team, and we expect him to perform well."

The decision to not risk Navas seems a wise one given the important matches on the horizon for PSG, as they go to Marseille on Sunday for Le Classique and have the first leg of their Champions League last-16 clash with Barcelona on February 16.

PSG reached the final of Europe's elite competition last season under Thomas Tuchel, though that seemingly only earned him a certain amount of credit given his recent dismissal.

Despite PSG's apparent fixation with the Champions League since their QSI takeover in 2011, Pochettino insists it is not his focus, instead urging his team to respond to the Lorient setback as they look to prioritise domestic success.

"We have to improve collectively," he said. "We lost the match in Lorient in two actions. We are looking for solutions.

"We do not have much time to train, but we discuss to try to find solutions. With my staff, we arrived with the circumstances that you know.

"We assume our great responsibility. The objective is to win, to optimise the team. We want to win Ligue 1, which is our priority objective and there is time to do so."

PSG head into the midweek round of fixtures sitting third in Ligue 1, three points adrift of pacesetters Lille.