My note about Futures Vero Beach'16 tournament that I worked at...Millman's coach, who when he was shown in the box last night, looked very familiar to me. Then Pat McEnroe gave me the answer why his face was ringing a bell...he played that tournament and I did his racquets all the way to his title win, including a SF win over Shapo. His name is Jonas Luetjen, from Germany and just turned 29 last month. That makes him almost two months younger than Millman.
Jonas was an extremely polite young man in my interaction with him. He was playing clay for the first time that year after playing indoor and outdoor HCs through the winter and early spring. After a couple more months of Futures tournaments without a title, he played several weeks in the German Bundesliga non-sanctioned tournaments and probably made more money than his entire year at the Futures.
I have to rate trying to succeed at Futures level as a cauldron not matched in other sports for the development of young talent. Shapo had just turned 17 when I met him and yet carried himself with overall poise you might associate with a man in his 20's or 30's. He obviously was traveling with a coach, being a teenager. Same for Kecmanovic that week. Both teens were quite adjusted to lifestyles in Florida, with Kec training here in Bradenton and Shapo having spent the previous fall and winter down here grinding from 128-man qualies into and actually winning Futures main draws. Jonas was several years older (26) and had done the college route here in the Southeast U.S.
Some of these participants mentioned by OP may be going through their first experiences a long way from home and it takes a while to adjust and open up. Having someone that is familiar with home, even if it's a dusty unused bit of broken dialogue in their native tongue, can break the ice. I know that from personal experience. When both Gerald Melzer (Austrian) and Luetjen introduced themselves, I asked in English where they were from. When they answered, I spoke a short sentence in German I still retain from having lived in Germany and taking two years of classes for the language in college. It made for smooth interaction both times! The rest of our communication was in English but we had become more comfortable with each other. Same for a pair of German dubs players, a NCAA champion from Germany and his French coach, a lot of the Italian players I met (lived there for three years) and the very few French players I encountered (lived there too).