Mirra Andreeva, Vicky Mboko, João Fonseca and Learner Tien are teens to watch at the US Open

NEW YORK (AP) — There is a fascination in all sports — all walks of life, maybe — with young stars, those such as tennis player Mirra Andreeva, a Russian who is still only 18 yet already has been a Grand Slam semifinalist and is seeded No. 5 at the U.S. Open as it begins Sunday. Or João Fonseca, a...