Leaning towards an AMC, let's say David Silva type of MC. Pellegrini will be great together with a hardworking tackler, something I find perfect in an attacking setup with his great key passes, crosses and dribbling. He shouldn't really be compared to a lot of the other players discussed. Just some stats to explain:
Player - Tackles/Interceptions/Clearances/Blocks/Dispossessed/Bad Control (Per game)
Herrera -- 2,5 / 2,1 / 1,3 / 0,4 / 0,4 / 0,6
Neves ---- 2,3 / 2,1 / 1,0 / 0,6 / 0,8 / 0,9
Ndidi ----- 3,2 / 1,9 / 2,2 / 0,2 / 1,0 / 1,7
Lemina --- 2,6 / 2,2 / 1,4 / 0,2 / 1,6 / 1,2
Matic ----- 1,8 / 1,3 / 2,0 / 0,6 / 1,4 / 1,0
Barella --- 3,2 / 1,4 / 0,8 / 0,1 / 2,0 / 3,2
Pellegrini - 1,8 / 0,3 / 1,0 / 0,1 / 1,7 / 1,9
Pellegrini isn't even close to match the defensive stats to the others. Herrera with outstanding numbers.
Player (Goals/Assist) - Shots/Key Passes/Dribbles/Crosses/Long Balls/Through Balls (Per game)
Pellegrini (1/3) - 1,6 / 2,6 / 0,9 / 1,6 / 0,9 / 0,2
Neves (3/2) ---- 2,4 / 0,8 / 0,3 / 0,2 / 6,5 / 0
Barella (1/0) ---- 1,4 / 1,0 / 0,9 / 0,6 / 3,0 / 0,1
Herrera (2/3) --- 0,9 / 0,8 / 0,4 / 0,1 / 1,6 / 0,1
Ndidi (2/0) ------ 1,8 / 0,6 / 0,9 / 0,0 / 2,7 / 0,1
Lemina (0/1) --- 1,2 / 0,5 / 1,1 / 0,2 / 2,2 / 0
Matic (1/0) ------ 0,5 / 0,5 / 0,7 / 0,1 / 4,3 / 0
And here the opposite, the 2,6 Key Passes per game, 1,6 Crosses and 0,2 Through Balls are unmatched. Clearly a player that compliments Herrera/Matic. He would be what Silva is next to Fernandinho, only 11 years younger and obviously not as good (yet).
Neves the standout player when you look at all stats combined, but he also cost 3 times as much as Pellegrini.