Liam Rosenior has vowed that Chelsea will conduct a full investigation to discover how his starting line-up for the Champions League clash against Paris Saint-Germain was leaked online eight hours prior to kick-off. The Blues' tactical plans were circulating on social media throughout Wednesday afternoon after being initially reported by a French journalist, including the surprise news that Filip Jorgensen would start over Robert Sanchez.French reporter Fabrice Hawkins was the first to publish the Chelsea starting XI on social media, exposing Rosenior's hand and tactical adjustments long before the players even arrived at the Parc des Princes. This unexpected drop of information ultimately stripped the Blues of any element of surprise heading into a crucial European tie.Speaking after the heavy 5-2 defeat, Rosenior admitted he was in the dark regarding the security breach during his pre-match preparations. “I wasn’t aware,” he noted after the game when informed of the leak, as per Daily Mail. “I’m sure we’ll get to the bottom of that if that’s the case. These things now, they happen quite a lot. We get information about our opposition. I’m more worried about the end result than the beginning of the game.”The decision to start Jorgensen proved to be a turning point in the match as the 23-year-old was at the heart of the defensive collapse. With the score level at 2-2, the Danish goalkeeper committed a high-profile error while attempting to play out from the back, allowing Vitinha to lob the ball back into an empty net to restore the Parisian lead. This sparked a flurry of late goals that has left Chelsea's European campaign in tatters.Despite the costly error, Rosenior steadfastly defended his decision to rotate and shielded the goalkeeper from taking the brunt of the blame, stating: “Players make mistakes. Filip's not the first one to make a mistake. And that's part of football. I make mistakes. Everybody makes mistakes. Sometimes they’re more costly. This is one of those moments. What we have to do for Rob and for Filip and for all of the players is look after each other. This is a big test of our character."Add GOAL.com as a preferred source on Google to see more of our reportingChelsea must now regroup quickly before a vital Premier League clash against Newcastle this Saturday. With the club currently fifth in the table and fighting for a top-four finish, the pressure is mounting on Rosenior to find a solution to the defensive fragility. While PSG will enjoy a weekend off after having their Ligue 1 fixture postponed, Chelsea must find resilience immediately.