I think when we talk about the worth of a player to a team, it would be more relevant to compare a player's performance with the performance of other players with similar role in the team. In the case of Rooney, his worth to the team is more relevant to be judged based on his impact or contribution to the team, relative to the other attacking players in the team, rather than to compare it with some unclear standard, or his past performance.
I've always been excited whenever I saw Rooney's name in the starting line up, because I always felt that we are stronger with him in the team, and seemed to score more when he was playing. I was curious whether it was just my delusion or was there any evidence to support that. So I dig a bit and below is what i found.
I chose to compare matches when a player started and when he did not, to gauge his impact in a match, and disregard the matches when he were a sub, since the playing time were usually very short.
Numbers indicate Match-Win-Draw-Loss for competitive matches in this season until Hull City match today:
All matches : 37-22-9-6
Rooney start : 18-15-0-3 (83% win ratio)
Rooney did not start : 19-7-9-3 (37% win ratio)
Rooney started in 8 of the 10 matches in which United scored more than 2 goals.
Martial start : 16-10-3-3 (63% win ratio)
Martial did not start: 21-12-6-3 (57% win ratio)
Martial started in 5 of the 10 matches in which United scored more than 2 goals.
Mata start : 21-15-5-1 (71% win ratio)
Mata did not start: 16-7-4-5 (44% win ratio)
Mata started in 8 of the 10 matches in which United scored more than 2 goals.
I counted the numbers manually from fixtures and results stats in manutd.com, please cmiiw.
For me, the stats above does not support the opinion that United played better without Rooney, and there is actually a possible reason for Jose to play him in some matches instead of Martial or Mata.
What about the past 3 seasons? Well, Rooney was our top scorer in 2013/14 and 2014/15, and second highest scorer after Martial in 2015/16. The question is, if Rooney was poor, how about the other attackers that we had, did they do any better? If they did, how and by what standard? If most players did not play well after Sir Alex left, what is the point of focusing on one player’s poor performance during the period?
And by the way, before somebody mention it, I think his 260k a week salary is as relevant as the 515m record revenue United just announced recently. We don’t have to free it up to pay for several world class players if we can attract them to play for us.