I think Holtby could perform alongside Sandro and give a blend of Parker's crazy closing down and Carrick's passing.
Honestly can't see what Carrick does better defensively than Sandro. Sandro tackles and intercepts more.
Here are some stats.
Sandro averaged 3.6 intercepts per game this season and Carrick averages 2.4 intercepts per game this season in the PL.
Sandro averaged 3.3 tackles per game this season and Carrick averages 2.3 tackles per game this season in the PL.
So what does Carrick do as this 'intercepting DM' that makes him superior?
http://www.whoscored.com/Players/2115
http://www.whoscored.com/Players/68890
I seem to remember that Carrick was only rated at the end of his spell with us. Wasn't he one of the most slated players due to his languid style and apparent lack of work rate, and the origin of "[insert player name], what does he do"? He was certainly rated post-Spurs, and rightly so, as the void after him was there for all to see. But I for one remember Spurs fans jerking each other off for Ferguson being stupid enough to pay 16M or thereabouts for him, it was only in hindsight that the majority "rated him highly". If my memory serves me correctly.