SPRINGFIELD, Ill. — Tariq Toran, the coach of the Central Illinois Xpress basketball team, presented his players with matching mouth guards for Christmas. He had made sure they all came in fluorescent green.

The Xpress were already drawing attention, having emerged as an unlikely force in the fifth-grade boys’ league at the Gym, a bustling basketball center here. In running their record to 8-1 through the first half of the season, the Xpress executed a motion offense and often overwhelmed the competition. But they really stood out for another reason.

“We’d walk in, and all the boys would be like, ‘We’re playing girls?’ ” said Anne Rupnik, a point guard. “Then we’d beat them. Some of them cried.”

The players go by nicknames like Koko, Beans and Flash. They try to color-coordinate their socks. And they have gone about the hard business of winning basketball games — as the only team of girls in the league — with the cool, calculated approach of tax auditors.