I posted this in the tactics thread on /r/soccer but was waiting for the post game day thread over here.

I got thinking after the Chelsea-United game last night about how to best play with a man down.

Last night United started with a 4-5-1 with Jones as a CM and young as a defensive minded left midfielder.

After the red, Mikhitarian was replaced with Fellaini who took up Herrera's position in midfield. Very defensive but perhaps it was the right call against a Chelsea team who could have scored a lot of goals against United. The biggest issue was that United had no threat on the counter which was essentially the only option to create chances. And having Jones and Fellaini as CMs meant United had no quality passing out of their own half.

My thinking was that a double change of Fellaini for Mikhitarian (or better still Rashford as he's less experienced and was ill) and Carrick for Darmian. Then switch to 3 at the back with Fellaini and Carrick holding in front and Young as a left wingback. This option would have given United Carrick as a passing option to start counter attacks and with Young and Valencia as wing backs there would have been a greater attacking threat without compromising the defence too greatly (Fellaini covering). With Pogba pushing forward his contribution to the game could have been greater.

I remember watching Mancini's City switch to wing backs when a man down vs United and they were a huge threat, coming back from 3-0 down to 3-2 with 10 men iirc. Just something to think about.

Edit: An old article from The Guardian by Micheal Cox about Mancini's tactical change with 10 men.