Javier Pastore's move to Paris Saint-Germain has been a roller coaster. It was unlikely, then likely, then official and now back to likely, but odds are it's happening. When it was initially unlikely it was because it looked like the Argentine midfielder was on his way to Stamford Bridge to play with Chelsea. The Blues' bids for Luka Modric were denied and especially with Michael Essien out with a knee injury they needed a midfielder so losing out on Pastore hurts.
Now Chelsea has to move on and figure out how they're going to fill out their squad before the transfer window closes. That probably means two more players, not just one. Graham MacAree of SB Nation's Chelsea blog We Ain't Got No History cautions Chelsea not to overreact to losing out on Pastore though.
At this point, I really hope that they don't rush into anything else. They've done probably the right thing in refusing to overpay for Pastore, but the squad still needs help in order to compete (I think), and I'm very worried that Chelsea will simply make a panic buy in order to patch up some holes. They need help in the middle and at least one right-sided player, but they're unlikely to find a better fit for the squad than Pastore.
There is talk that Chelsea will make another run at Modric, but that is the type of overreaction, overpaying that MacAree warns against. It may not be the big name, big money buy that Chelsea need, but two smart and dependable players. After all, they have to deal with Essien's absence, but he does figure he be back before the end of the season and Yossi Benayoun will be back for the year so they are hardly helpless in the midfield. They just need some shoring up.