Chelsea boss Liam Rosenior has leapt to the defence of Robert Sanchez despite a shaky performance from the goalkeeper in Sunday's 2-1 defeat to Arsenal. The Spaniard found himself under intense scrutiny at the Emirates Stadium after misjudging a cross for the Gunners' winning goal, but his manager insists the blame should not rest on one man's shoulders.Speaking at Cobham ahead of a midweek trip away to Aston Villa, Rosenior addressed the criticism aimed at his goalkeeper following the London derby loss. He stated: "I think each player adds to the overall picture and functionality of your team. So yes, the first few minutes we had a few nervy spells. The fact that we played out from the back affected their press and gave us space in the areas that we wanted to have those spaces. I think that's just as clear. So I don't want to single out players and say what they can or can't improve. It's about the functionality of the team. I don't think anyone can say in the moment, other than the two set play goals, my team did not function well in the game. By the way, the league leaders, top of the Champions League. We functioned in a very good way for a lot of the game. The reason we lost the game was we didn't take care of the moments. Nothing to do with Rob's build, nothing to do with the way that we played. We have to manage those moments to win games of football."The defeat was further compounded by a moment of madness from Pedro Neto, who received a red card for two quick-fire bookings, including one for dissent. The dismissal sparked a fierce reaction from pundits, with former Blues striker Chris Sutton branding the winger an "idiot" for letting his team-mates down. However, Rosenior revealed that the former Wolves man has already taken steps to make amends in the dressing room as the club looks to move past their ninth dismissal of the season.Rosenior explained the internal fallout from the red card, saying: "It needs to improve. My job is to create a culture of accountability. If you make a mistake, you have to hold your hands up to make sure it never happens again. You need teammates to help you but it comes down to yourself as well. Pedro has apologised to the group. I need to see an improvement in the behaviour now. It's not just Pedro. Enzo [Fernandez] is a top leader. It's something that needs to improve. We are one of the youngest teams in Europe. Sometimes you need to go through experiences to improve. I don't want it to be a learning experience where we fail to achieve what we want to achieve."Chelsea’s disciplinary record has become a major talking point in the Premier League, with the club racking up cards at an alarming rate. Rosenior admitted that he is looking for a "deep-lying" cause for the team's lack of focus in high-pressure moments. He warned his squad that future team selections could be heavily influenced by a player's ability to stay on the pitch, as the Blues cannot afford to continue playing with ten men if they wish to climb the table.The manager added: "It's showing the value of not having a red card is. Our percentage chance of winning goes through the roof. Reacting to setbacks, sometimes it's giving the ball away, sometimes it's the referee making a decision you disagree with. You pick players who are showing that improvement. I can't afford to go through a season where there is a red card in every two or three games. I need to do my team selection based on that."Add GOAL.com as a preferred source on Google to see more of our reportingChelsea now face a quick turnaround as they prepare to visit an Aston Villa side looking to bounce back from their own recent setbacks. Unai Emery’s side have been clinical in front of goal, and Rosenior is fully aware of the threat they pose to a Chelsea defence that has looked vulnerable from set-pieces lately. With Villa known for their attacking prowess, the Blues will need a flawless performance from Sanchez and his backline to secure a result.Laying out the challenge ahead, Rosenior concluded: "The reason Villa score great goals is because they have great attacking players. It will be a very difficult game. They're very clinical in terms of the expected goals they create. They are going to have a reaction from their last result so we will prepare for a very difficult game."