You don't need strength my lad. You need wisdom.
By no stretch of the imagination did we "completely outplay" Sunderland. Had we done so, we would have won. We won the possession and we took 26 shots, but the stats don't tell the whole story - why did we have more possession and more shots? Because they parked the bus once they were ahead, daring us to have a go at them and risk being hit on the counter. We didn't take the risk and instead restricted ourselves to long shots from outside the area. We failed to break down the bottom team in the division. It's that simple.
Pienaar has been pretty good (not brilliant) most of the season, but was poor yesterday. Martinez saw fit to sub him, so maybe I'm closer to being right than you are on that point. Mirallas has been hot and cold all season - I'm still waiting to see the same Mirallas who was tearing the RS a new one in the derby last year prior to Suarez stamping on him. We are simply not giving Lukaku any quality ball - he was out on the right wing several times in the second half ffs - and Pienaar and Mirallas are two people who I expect to be providing that quality ball but they aren't doing it, and haven't done for several games. Be it a loss of form or simple fatigue, they need someone else sharing the load - that's why Deulofeu was loaned in the first place.
How many times did McCarthy burst forward into the box yesterday? How many shots did he have? He covered a lot of ground, yes, but what creativity, guile or offensive threat did he provide? We NEEDED someone other than Barkley and our fullbacks to step up yesterday, to provide an alternative means of attack: no-one did.
Donovan has proved that he can play prem-level football, and is likely available on a cheap loan for long enough to cover until Deulofeu returns. If Deulofeu was fit, I'd not be asking for Donovan; if we had squillions in the bank to sign a marquee player, I'd not be asking for Donovan. If we had a sub who was as good as him or better, I'd not be asking for Donovan. However we are pi$$-poor, our squad depth out wide is Naismith and then nothing, and we just lost to the bottom-placed team in the league. Having the highest-scoring defender in the prem isn't making all those problems go away.
Having a brain and using it is not "knee-jerking" pal. We need a couple of starter-quality additions to maintain our position, because we cannot handle even two or three injuries and suspensions with a squad as thin as we currently have. The proof of that is yesterday's loss.