Which MLS teams have underperformed and overperformed so far?

We're now a quarter of the way through the 2018 MLS regular season and with that, some trends are beginning to develop across the league.

Every team has played somewhere between seven to 10 matches so far, which in the grand scheme of things is still a pretty small sample size. But looking at expected goals (or xG) data provided by Opta, we can start answering some questions about whether a team's fast start is for real or if a slow one means doom for another.

Expected goals tell us the amount of goals a team should score on average based on their quality of chances. It's been a common theme this season, but looking at those numbers tell us that the Philadelphia Union should have more goals.

When looking at the table, note that negative numbers means a team is slightly underperforming based on their chances while a positive one means they're slightly overperforming. A number of factors could be contributing to this including luck, finishing and goalkeeping.

One trend that should be noted is the fact that the highest-scoring teams in the league (ATL, SKC, RBNY, NYCFC, LAFC) all have xG numbers in line with their goalscoring totals. It wouldn't be a surprise to see these teams continue at the rate they're going. Also, while Seattle seem to be in a downward spiral, their 1.48 expected goals per game are tied for 12th in MLS.

Looking at the defensive side of things, expected goals against (or xGA) tells us the amount of goals a team should have allowed on average based on the quality of chances they conceded. Like the table above, the difference between the two numbers could relate to a number of factors. 

For the table above, teams that have a positive GA-xGA figure have underperformed defensively while teams with a negative GA-xGA number have overperformed. Real Salt Lake should be very concerned about their defense, as the 2.51 xGA per game they have conceded is the most in MLS.

If you are looking for a regression candidate, a team that could be seeing less-positive results soon, New England could be the pick. Both their attack and defense are overperforming based on the quality of chances they have created and conceded. On the other end, Columbus and the Union could be do for some better results ahead as they are both underperforming in the attack and defense.