FC Dallas as an organization puts a lot of emphasis on the Lamar Hunt US Open Cup, after all, it's named after their late owner. But that doesn't mean the club won't use the games against lower division opposition - which New Mexico United is, being a USL Championship side - as a chance to test some reserves and youngsters.
Unfortunately for FC Dallas, New Mexico United is also quite a good team and was in first place in USL West until earlier this week. So when FCD's younger team came out flat in the first half and were unable to get it going until late, it wasn't enough and New Mexico took advantage for the win.