Do you have Bobby's stats for the 4 years also and not just the last two as with Mane ?
Last 8GP: 4 goals + 2 assists = 6 involvements in 442 mins for
73.7 mins per goal involvement.
2020/21: 9 goals + 7 assists = 16 involvements in 2852 mins for
178.3 mins per goal involvement.
2019/20: 9 goals + 8 assists = 17 involvements in 3004 mins for
176.7 mins per goal involvement.
2018/19: 12 goals + 7 assists = 19 involvements in 2620 mins for
137.9 mins per goal involvement.
2017/18: 15 goals + 7 assists = 22 involvements in 2778 mins for
126.3 mins per goal involvement.
2016/17: 11 goals + 10 assists = 21 involvements in 3068 mins for
146.1 mins per goal involvement.
2015/16: 10 goals + 8 assists = 18 involvements in 1983 mins for
110.2 mins per goal involvement.
Firmino in his last 8 games is in the form of his life
That said, 8 games is a very small sample size admittedly, and it's also across two seasons so it's not super reliable.
It is absolutely concerning that his production levels have dropped from his first four years under Klopp where he was consistently having a goal involvement every 110-140 minutes, as compared to the last two years when he's had a goal involvement roughly every 177 minutes.
It's pretty clear looking at these numbers why he's the one who's getting dropped more frequently for Jota. However, as I mentioned in an earlier post, even though Firmino has taken a step back in terms of production, upgrading our 4th striker from Origi to Jota more than offsets the drop in production by Firmino (and Mané).
For the record Jota produced 9 goals in 1112 mins last year for a goal involvement every 123.6 minutes.
Effectively Jota has replaced Firmino as the 3rd forward option (i.e. Jota's goal involvement every 123.6mins has replaced what Firmino was producing), and Firmino has replaced Origi as the 4th choice forward - an obvious upgrade.
It's worth noting that this team won the league with 98 points even when Firmino's goal involvement rose to ~177mins/involvement, so it's not as if the team can't be successful even if he continues playing as he has done the last 2 years.
Anyways, to go back to the point of this conversation, this team is absolutely better overall (at least on paper) than the 2019/20 team, as the additions of Thiago, Jota, Konate, etc and improvements from Jones, Elliott, etc more than offset the losses of Wijnaldum or any perceived loss of form by Firmino or Mane.