A luxury player at best. Yes he scores goals and has all these nice numbers and statistics going for him but fact is his inclusion week in week out is hindering our team. You need 11 players that play well as a cohesive unit - not a smattering of individuals that don't play well as a unit. After all it is a team game - not a game of 11 technically decent individuals. Remember Asprilla at Newcastle back in the day? Yes he was a very good player, but his inclusion made the team suffer.
Sigurdsson got all these impressive numbers at Swansea because the team was built around him - he was the only player they really relied on for goals and assists, and they were built to his strengths. He played in a completely different system where he was the main man, and now he's getting exposed somewhat where he now has to act as part of a system, instead of being the system. And as we've seen many times throughout PL history, building your team around 1 player is rarely a good idea if you want to be successful.
He needs replacing for sure, but problem is his only replacement is Davies who quite simply won't cut it at this level. Badly need a good technically decent midfielder in who has the skillset to play in a 4-3-3, which Sig doesn't.