Maybe in their other title winning seasons but definitely not this season because they did reinforce in the summer. They spent the second most cash in the EPL on five first team players; a CB, two CMs, a wingback and a striker, which is more than we, Arsenal, Liverpool and Tottenham signed despite finishing 5, 4, 3 and 1 places below them respectively. You could say they sold or loaned the players who were supposed to be back-ups, but thats not entirely the case. At the start of last season, they had Azpi, Cahill, Luiz and Terry as CBs. At the start of this season they have Christeinsein and Rudiger over Terry. Thats an improvement at CB. At wingback, they had Azpi, Moses and Alonso, now they have Zappa and Kennedy in addition to those three. In midfield, they had Kante, Matic, Chalobah, Fab and RLC, now they have Baka, DD, Kante and Fab. They are at a disadvantage in midfield this season, but thats not entirely the case when you consider the fact Chalobah played just 2 games(at the end of the season). In attack, they have exactly the same players they won the league with, with Morata for Costa the exception. Begovic left and was replaced by Caballero. The notion that chelsea didn't reinforce the squad 'adequately' is IMO, false. One problem is, they where lucky with injuries last season, unlike this season and just as it was for Raneiri and Leicester, Conte doesn't seem to have the same chemistry he had with the players last season. Reinforcement is not the reason they keep making poor errors at the back despite having the exact same defenders they won the league with, and even upgraded the CB that played the least minutes. They lost Matic, and spent 80m to replace him; they lost Costa, and spent 58m to replace him. They strengthened the wingback and CB positions at a cost of 54m, but Conte cant stop whining. The problem is the manager, the players, title winners syndrome and other factors beyond our control(injuries, UCL) not what we are being led to believe.