While Messi has made some significant progress in his attempted return from injury, the club needs to be prepared for the event that Messi can't start the biggest match of the season. In that case, Barcelona's standard 4-3-3 may not be the best option for the starting XI - and other options should be investigated.
There's been a lot of positive news to come out of Barcelona over the international break. Aside from the injury scare Sergio Busquets has faced, the club has had nothing but very, very good news - including the great Lionel Messi joining the squad in full training with less than a week to go until El Clasico.