Funny LSP, because I am not normally one who believes in "the older ways" of handling pitching staffs, but there is one exception that relates to this, in years past if a manager ran out of bullpen arms he would simply use a starter to "finish" an extra innings game. No manager would do that today, but I would and think it is reasonable.
There is no reason why you could not go to tomorrows starter and say "the game is yours". If he ends up going just 1-2 innings then you re-arrange the starting order so he starts again in a few days. If he goes say 7 innings then you either have to find an off day to re-adjust your starters or have a reliever game in a few days.
I get that starters dont like this, they want to start when they are scheduled, but the sport is unpredictable. Rainouts happen also, that also changes what they have to do.
That is what I would have done if there were no relievers left.. but, there were.
Gomez gave them 1 good inning in a high leverage situation. To me it was a mistake to put him in that position, but to push the luck for a 2nd inning against the middle of the lineup was incompetence, pure and simple. Gomez is a workable reliever, but he is not only in a slump but he is obviously had his confidence shaken. Put him in the 7th inning group, dont keep using him as a primary reliever, let him have some good outings and then move him into a setup role, but dont keep throwing him out there with his confidence on the line.
Mac was never a manager before, and I think we can see why, he just isnt a good one. One could argue that it doesnt really matter, but if this is not the guy that we think should manage a contending team why on earth would we want to keep him around? Get a better manager and let him grow with the team and who knows, maybe he will have a Charlie Manuel moment and actually get talented players to play better, even if he does not understand how to make a double switch 
