You could make an argument that Chad Marshall is the greatest MLS player of all time in any position. A centre-back would never be adorned in such a lucious manner, but such has been the consistency, quality and impact of his performances, he could very much be considered in such high esteem without much quarrel. Marshall was named to the MLS Best XI in 2014 and 2018, won the Defender of the Year award in 2014, and was a crucial part of one of the best defences in MLS of the past decade in Seattle.
His partner in this team of the decade, Omar Gonzalez, has been equally as dominant. Anchoring the great LA Galaxy teams early in the decade, Gonzalez has won three MLS Cups, was named the Defender of the Year in 2011 and was phenomenally named to four MLS Best XIs in five years between 2010 to 2014, missing out in 2012 when he played only half the games due to a loan to Europe and almost immediate ACL tear. He was also made the first DP centre-back in MLS history in 2013.
Collectively, of the ten MLS Cups to be played in this decade, six included at least one of Gonzalez or Marshall. You will not find a clearer illustration of their collective dominance of MLS over the past ten years.
Honourable Mentions: Matt Besler, Ike Opara