Usually match officials are the ones facilitating substitutions. In Week 1 of the 2019 season, one referee had to request one.
Assistant referee Kevin Klinger, who was manning the far sideline at Orlando City Stadium, was forced to motion for a sub in the first half after suffering what looked like a muscle injury.
The substitution was swift, however, as fourth official Malik Badawi swapped places with Klinger and the match proceeded shortly thereafter.