He became a quadriplegic at age 21 while visiting a friend in Redondo Beach, California, during summer break.

[6] In 2007, he participated in the first Quad competition held at the U.S. Open, winning doubles with Taylor and taking second place in singles behind Peter Norfolk.

[7] Wagner had urged the United States Tennis Association to include a quadriplegic division at the event; the U.S. Open was the first of the Grand Slam tournaments to do so.

The Australian Open followed suit the next year, with Wagner finishing runner-up in singles, and winning doubles with Taylor.

[11] Wagner, partnering Alcott, won the inaugural Roland Garros Quad Doubles draw.

[6] At the 2012 London Paralympics, Wagner and Taylor won one more gold medal in doubles, defeating the British team of Andy Lapthorne and Peter Norfolk in the final.

[1] Wagner had been crowned doubles champion at every U.S. Open Quad Doubles draw, since the Grand Slam started offering a Quad Draw, in 2007, until 2019, when Wagner with partner Bryan Barten lost to Alcott and Lapthorne.

Besides competing, Wagner is often invited to teach in wheelchair camps and clinics in the United States, where he encourages both kids and adults to become involved with the sport.