I found this nice chart on the average position of each player.
Everton v Manchester United: live - Telegraph [click the 'team stats' tab on the chart on the right]
It looks something like this:
......................1......................
..............................................
...............15..........6................
..............................................
......4......13......24................3..
..........................23.................
.......................10.14................
......................................19.....
So it actually looks like Rooney was more on our right than Chicharito, though even Rooney is slightly to our left overall. Park, Vidic and Jones are the only starters to spend more time on our left than our right!
I could see that looking like a 4312 based on that.
Jones Vidic Evan Evra
.....Park....Fletcher
.........Cleverley
..........Rooney
......Chich....Welbeck
I get the idea that players don't play as much in formations as we think. But I'll happily bow to anyone who claims a strong understanding of formations. I can see 4141 makes sense too.