This stats below clearly show that our defense was still good even when we have Fred and no Matic. The fact is that our form is improved because Bruno came in to solve the lack of creativity while our defense was always been similar with or without Matic.
This is the period when we had Fred but no Matic, we had 13.97 xGA (expected goal against).
This is the period when Matic came back into the team, we had 18.56 xGA.
Don't mean to derail the conversation regarding Fred, but I thought these stats were quite interesting.
If you normalize by matches, xGA is 1.16 per match in the period with Fred but no Matic, and 0.97 with Matic back in the team. Not a large difference at all.
On the offensive side, xG remained relatively similar as well (slight decrease in fact) at 1.82 in the period with Fred but no Matic, and 1.74 with Matic back in the team. So, our expected goals actually decreased in the second period.
The interesting part is how we performed relative to expectation in the two periods. In your first chart, we had 1.73 xPTS per game, but underperformed, earning only 1.58 pts per game. In the second chart, xPTS were marginally higher at 1.88 per game, however we exceeded the expectation earning 2 points per game in the period.
Essentially, we under performed in the first period and over performed in the second period, relative to expectation. I think the concerning bit is that our xG slightly decreased in the second period which makes me wonder if we really did "solve the lack of creativity" with the addition of Bruno or if we just had a "luckier" period.