There's a related point that has been made by you, me, Dreamy, Fox and a few others, about the conversion of chances in games when they are at a premium, and the value that a supremely clinical match-winner or goalscorer/ whatever can add to the team when you are only going to get one chance, and you may have to make it on your own. When you "nick" a result.
The other unanswered - and currently unanswerable - question is if the total number of goals scored as a team would be increased or decreased if Firmino was replaced, or playing a different role, but obviously it may be that that replacement isn't actually at the club yet. If you look at obvious metrics like goals scored and assists, then Firmino has a mediocre return; 6 goals and 2 assists in the Premiership. But the work-rate and overall contribution to the team's performance is harder to measure, especially given there isn't a satisfactory "control" to provide a benchmark.
Firmino has 6 goals, which is a goal every 296 minutes, so he's been outscored by all the players you would expect to outscore him - Sanchez, Costa, Ibrahimovic, Kane, Lukaku, Defoe, Aguero, Hazard, Mane, Dele Alli, Benteke, Giroud etc - but also Snodgrass, Lallana, Antonio, Rondon.
But it also means he also has the lowest goal/ minute return of any attacker in the league*, and a worse return than Callum wilson, Fernando Llorente, Son Heung-Min and Charlie Austin, who have all scored 6 goals in less minutes.
So while you could put almost any striker into our team and get more individual goals, it is hard to say that this would mean we win more games, or score more goals overall, because what you might lose in workrate and the ability to force a corner from a mistake, or whatever, is harder to gauge.
So using Dreamy's favourite player, Defoe, for example, he's obviously a far superior finisher, but he doesn't have anywhere near the stamina, workrate and variety of movement into channels, or that understanding with his team-mates, especially Coutinho.
Like everyone, I genuinely do not care who scores, as long as we win. My issue with Firmino - and many others before him, like Crouch - is that for all the value and contribution to the team, elite football is a game of fine margins. Of maximising opportunity to win.
And as I've said on many occasions, while the best defence or the best striker is in NO WAY an essential factor in winning a title, if you look at the last 10-15 years of Champions, the team who has won it - in 80% of examples - had a player who has scored in and around 20 goals. So you're more likely to win it if you have one. Quite obviously.
We could win it with a player who scores 10-12 as a top scorer. It's just far less likely.
*only counting those that have 5 goals or more.
