The Sky Sports pundit has had his say on Chelsea manager Jose Mourinho's best buy at Stamford Bridge.
The Portuguese boss has brought in a host of players during his two stints in charge at Stamford Bridge, but Carragher believes the addition of the Serbian is his most notable piece of business.
Matic was signed by Mourinho at the start of the calendar year from Benfica for £21 million and the former Liverpool defender believes it was a deal which even surpasses the transfers which saw Diego Costa and Cesc Fabregas arrived at Stamford Bridge.
Matic has been an ever present ever since singing at Chelsea for a second time and has established his position as the best holding midfielder in the Premier League.
Combative yet creative, he offers great amounts of protection to the Blues' defence, but also drives them forward and is likely one of the first names on the team sheet for the London club.
Chelsea have lost just once this season - to Newcastle United - and it is no coincidence that Matic was not in the team for this match.
The Serbian is an irreplaceable player in their starting line-up and nobody will be more important than him if they are to be successful in claiming the title come May.