I think Marco got it right in the first. Only chances they had were because our CBs stink - although Zouma played well in spurts. Only reason we didn't have better chances is because our CF stinks. But the formation killed Watford's 4-2-2-2 and prevented them from attacking centrally.
Beyond that, YOU WOULD THINK an experienced ref could tell when a team was tactically fouling and administer a yellow cared before the 69th minute. It was ridiculous. They must've had 20+ fouls.
Unfortunately, Marco didn't make proper adjustments when Gray came on at half. They completely changed the point of attack, forced the ball wide, and created a ton of chances from the point Gylfi hit the bar until they scored. We morphed back into a 4-3-2-1, but without a midfielder that could play wider on the left and got gashed. Subbing Walcott was probably the right move considering what we had on our sorry bench - giving us the other wide player we needed, but it was too late I guess.
We had by far the better of play after that, but it was too late, they were packed in, and we simply don't have the ability to unlock these guys, although Digne just missed on the free kick. Pretty harsh result, especially after that first half, but you get THAT disorganized in the back that's what happened. Sure, it shouldn't have been a corner and frankly, shouldn't have been a free kick prior to that because Digne never touched that Watford player. But that stuff happens.
I am much more disappointed that we didn't score than the fact we gave up a goal.