Partey has been one of our best players on an individual level but we've sacrificed the defensive solidity that Rice offered, and we can't high up the pitch because he doesn't have the legs to defend transitions.
Since he returned to the team we've played 16 league games (I omitted the 3 red card games so it's only factors in 13 games), in which we gave up an average of 0.8 xGA. The previous 13 league games? An average of 0.5 xGA.
Yes, there are other factors at play such as the opposition not being identical between the two sets of results, but still nearly double the xGA is significant.