Set pieces are an extremely important part of any team's game plan heading into a match. They can change the course of a match in a matter of seconds, and if your team is prepared, they can be the basis of a teams success throughout a match or season.

Some teams have used this passage of play more to their advantage than others this season, with two teams from the Western Conference standing above the rest.

Vancouver Whitecaps FC and the Houston Dynamo have each scored seven goals off of set pieces this season according to Opta, which ties them for the most of any team in MLS this season. They haven't been too bad defensively either, each conceding three set-piece goals. Their +4 margin on set pieces is tops in the league.

It also appears that they are not vastly overperforming on these plays. Their expected goals numbers show that they should be among the best on set pieces. Vancouver's offensive set plays have collected an xG value of 5.44, meaning they would be expected to score 5.44 goals on average based on their quality of chances. That number is the highest in MLS and is just a bit more than Houston's xG value of 4.36, which is fifth in MLS.

Houston has been the better defensive team on set plays, allowing an expected goals value of just 2.37. That number is second behind the Philadelphia Union's 2.32. Vancouver's figure of 3.13 is in the top ten in the league.

When accounting for the differing amount of games played, you can see that these two teams are the best in MLS.

Team (xG For-xG against)/Games played VAN .18 HOU .13 SEA .13 NYC .10 NY .08

If you're wondering which team has struggled in this phase of play, it would be Atlanta United. They have yet to score a goal off of a set play this season and have conceded four. Their offensive set play expected goals value of 1.6 is the lowest in MLS and their defensive value of 4.72 is the second highest.

Two important notes before looking at Week 15's xG numbers: Penalties have a value of .79, and own goals are not factored into the values.