It also depends on player type, slow old-school players like tall target-man strikers or towering CBs can return fine but athletic players or players who creates miracle in small spaces suffers mostly. Unfortunately, for our case I am worried about Millar most, since he was a dribbler that plays with a lot small steps that requires change of direction, rotation.
One common thing is, usually they suffer same injury on other knee due to balance issues between knees. An article about it:
https://bjsm.bmj.com/content/55/23/1350
The second ACL injury rate in professional male football players is high, affecting almost one out of five players over an average of 5 years. Having sustained an index non-contact injury or isolated ACL injury were both independent risk factors for second ACL injury, and these two factors combined were associated with a 42% s ACL injury rate. The median career length following RTT was 3.4 years and 60% of players still played top-level football 5 years after ACLR.