Not interested i'm not sure, but not stretched or challenged is the problem. He's an automatic selection and anyone who knows anything about sports professionals is that they are competitive, take that away and they become lazy, unenthusiastic and demotivated. If he plays a really poor game...
Dave hasn't missed a penalty for the club, Ulloa has missed them previously and is not on form, apart from JFC for Buckley I found the substitutions strange. It appears that whenever the North Stand sings Lua Lua the manager responds. In response to your question there was no need to take Dave off.
The lack of strikers is a strategic failing on behalf of the club management, the manager has very limited choices, with Barnes gone the scramble for a replacement was lamentable and brought us Obika and now Jesse, neither are what we want. The slump has actually coincided with Jesse arrival...
Well, he has no competition for his place so how he plays is of no consequence. He s not playing well or scoring consistently enough and as for the penalty, dreadful. Great tactical decision to take Dave off! I sometimes wonder just how clever football managers are!!!