Serghei summed it up perfectly, nothing special or sparkly but I think he will help the team immensely. If anything, at least we won't be so susceptible to the cross, even when we had Puyol that was a problem for us and that is one thing about Mathieu that will be good, he is very solid in the air.
Out of all the signings we've made, this by far is the most relieving. I don't expect us to get another CB but I'd really prefer if we got another so we could move Mascherano back into MF, where he is clearly the better player. Mascherano the CB and Mascherano the DM are literally night and day.
From what I've heard, the only other player we are being linked to is a young gun from Brazil by the name of Rodrigo Caio. From what I understand, he might start out on the B team a la Halilovic to make the transition a little smoother. On his Wiki page, it says he came up against and mainly won a battle against Neymar and if he can stop Neymar or at least contain him, that's impressive. Only problem is Sao Paulo also want 20 million for him lol.
Flavia, you heard/watched this kid at all? I don't mind the idea at all, particularly if he has the same kind of potential as a TS. First half of the season he could play with the B squad and if he is so good that he clearly needs to be in the squad then we could promote him into the first team for the run in 2015.
For me, all that remains is a young stud CB and the selling of Song. I've always been a big Afellay fan and like someone else mentioned earlier, I'll always remember him for that wicked cross he put into Messi's path against Madrid in the CL semi's. Deserves to stay and honestly if Rakitic is just an absolute flop here or he gets injured(doubt it but its a possibility), he could actually do well in one of the AM roles. He is a solid winger but I like him playing through the middle more. He has a cannon of a shot (why I was drooling over him so much when he was at Eindhoven) and I've always wanted to see him be in a position to hit screamers from 25-30 yards out.
Baby steps...