Your gripe is with Gomes and Gbamin, who dwelt on and gave the ball away continuously from about half an hour in. It doesn't look to me like this is the job Sigurdsson is given in the 4-2-3-1. He's much closer to the front 3 than the midfield (there's an average position chart from Palace going around showing that he was higher up the park than DCL). Not far off being a second striker. He's clearly asked to press as high as the striker and is probably pushed that high because we don't have a goalscorer in that position.
Which is perfectly fine. But surely you can see how then a midfield 2 is over ran? 1st half Gbamin and Gomes dictated the game. Watford and even Palace last week pressed our midfield 2 where we couldn't string passes together.
When we have a high percentage of possession, Siggy further up the field works in specific build ups.
We have 2 players for each position for the most part. Each offering different things. We don't have that for Siggy. So when it doesn't work, where do we go? We don't. We leave him out there and are now relying on a very solid defence.
If we want to get higher up the league, we need options for when the game changes or we play a very defensive side.
