Not sure on this one to be honest Loki. At the time I was scratching my head as we did have the initiative having just scored and one would have hoped the confidence of the lads on the pitch would have pushed them on.
However looking at this from another side, it could be argued that BR felt it was time to put them to the sword by throwing more attacking minded players at them while they were down. In that sense it was a bold move, and it’s hard for anyone to say he took the easy way, or lacked initiative.
In fact Assaidi looked very direct, ran at their right back and could have been the difference. However Shelvey did not imo improve us, and while Allen may have been tiring (one possible guess on why he was withdrawn) he had done a very good job up till then keeping the ball moving and transitioning the ball from the back to the front. But then again a slight different trajectory on the ball JonJo fired into the side netting and he'd have been the hero and this thread would never have been started.
Bottom line for me, in hindsight the subs did not or could not change the outcome, however I'm not sure they were a mistake. We'll never know what would have happened if they had not been made, or even if they had been delayed by 10 minutes or so. Yes pulling Hendo and especially Allen opened up holes in our middle, which allowed Zenit more of the ball in our half but they did not or could not capitalize from that. However without putting on players willing to run at the Zenit back line it’s hard to say for sure keeping the original personnel would have been a better bet on getting the 4th goal.