Because it's like playing with 10 men.
We'd lost our momentum before Smith came on though...
Pardew's first substitute came too late, in my opinion, because like you say the momentum had begun to shift and the game was completely disjointed (due to a few injuries in a short period of time that held things up). They then made it 3-1 around 5 minutes after this, which led to my first complaint (to myself, admittedly).
In fairness, he then reacts with a decent enough sub, given that Fergie had progressively got quieter as the game played out and Lua Lua would provide a good outlet with his pace and dribbling ability (which he did on a few occasions), but soon lost the plot by bringing Smith on for Lovenkrands. Ameobi was a spent force by then, as usual, so I don't see why Ranger or Best couldn't have come on for him then and there. Lovenkrands was still looking lively to me. Pardew said himself this week that Smith would only be used "in an emergency", if I remember right, and this was far from it at the time.
Then I think it went 3-2 before Best came on for Guthrie, who probably was struggling by that point due to the fact it was his first game for a while after an injury, but which again proved to be a poor decision at the end of the day because it left Ameobi still toiling and we went on to concede yet another goal. Not to mention the fact that Smith was poor and Best was falling over a fair bit (despite looking lively).
Basically, with the benefit of hindsight added to what I was thinking while watching live, Lua Lua for Ferguson was fair enough but came too late, I then would have brought Ranger on for Ameobi and later Best/Kuqi on for Lovenkrands, depending on what the score was by then, and hoped that Guthrie could soldier through. We might still have drawn 3-3 or even lost 4-3, but I'm more confident we would have held on with those changes.
Just bizarre from Pardew, really, although the players do have to shoulder the majority of the blame - they are the ones out there struggling, at the end of the day.
Fair play.
While I personally wouldn't of brought Smith on, I can see his logic in a way, Guthrie was flagging and we were getting overran in the middle. I think he brought him on to be a ball winner but he just hid as usual.