In what way did it show that Arsenal have a greater strength in depth? If you look at the line-ups:
Man U: Arsenal:
GK: Van Der Sar (1st choice) GK: Almunia (2nd choice)
LB: Evra (1st choice) LB: Gibbs (2nd choice)
RB: Brown (2nd choice) RB: Sagna (1st choice)
CB: Smalling (2nd choice) CB: Djourou (1st/2nd choice)
CB: Vidic (1st choice) CB: Koscielny (1st/2nd choice)
LM: Fabio (2nd/3rd choice in that position) DM: Denilson (2nd choice)
RM: Rafael (2nd/3rd chioce in position) DM: Diaby (2nd choice)
CM: O'Shea (3rd/4th choice in position) AM: Wilshere (1st choice)
CM: Gibson (3rd choice) AM: Arshavin (1st/2nd choice)
ST: Rooney (1st choice) AM: Nasri (1st choice)
ST: Hernandez (1st/2nd choice) ST: Van Persie (1st choice)
Both teams have similar amounts of changes with Man Utd having at least 6 first teamers missing or on the bench i.e Ferdinand, Nani, Scholes, Fletcher, Valencia, Giggs as well as players playing out of position.
Arsenal had around 6 players missing as well i.e. Szczesny, Clichy, Vermaelen, Fabregas, Walcott, Song. So I would say that both teams showed good strength in depth but I feel Man Utd edged it with the stout defensive performance as well as cutting egde over Arsenal.
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VDS- First choice
Brown- Third choice behind Rafael and O'Shea
Smalling- Second or Third choice
Vidic- First Choice
Evra- First choice
Rafael- Fifth choice in that position behind Nani, Valencia, Park, Fletcher
O'shea-
Gibson- CM combination is 3123123123th choice.
Fabio- Fifth choice in that position behind Nani, Giggs, Park, Rooney
Rooney- First choice
Hernandez- Second choice behind Berbatov