Kupp attended Selah High School, where he competed in football, basketball and tennis. He didn't have a notable high school football career, so he wasn't highly recruited. He accepted a football scholarship from Montana Technological University, where he received All-Frontier Conference honors as a quarterback and punter. He transferred to Pacific Lutheran University after his freshman season, to complete his studies closer to his home. As a sophomore in 1987, he was a backup behind Jeff Yarnell and was a part of the NAIA Division II national championship team. As a junior in 1988, he became a starter at quarterback. His team eventually lost 35-56 in an NAIA Division II playoff game, after the Oregon Institute of Technology accomplished the biggest comeback in school history, by scoring 49 points in the second half. Kupp led his team to a 35-7 advantage at halftime, tallying a career-high 272 passing yards, 16-of-21 completions, 2 passing touchdowns and one rushing touchdown, before fracturing his left ankle with just two minutes left in the first half. As a senior in 1989, he made 185-of-286 pass completions for 2,398 yards, 25 touchdowns and 3 interceptions, setting the record for passing yards in a season and an NAIA Division II record for interception rate with a 1.04% mark. Against Southern Oregon University, he set school records for passing yards and touchdown throws in a single-game, while leading his team to a 52-50 win. He received All-Columbia Football Association honors at the end of the season. He finished his college career with 300-of-499 completions for 3,921 yards, 41 touchdowns and 11 interceptions. In 2003, he was inducted into the Pacific Lutheran Athletic Hall of Fame.
Kupp was selected by the New York Giants in the 5th round of the 1990 NFL Draft, he was the ninth quarterback taken. He was released before the start of the season on September 3, after not being able to pass Matt Cavanaugh on the depth chart.
Phoenix Cardinals
In September 1990, Kupp signed with Phoenix Cardinals and spent the rest of the year on the practice squad. In 1991, a training camp knee injury to starting quarterback Timm Rosenbach, allowed Kupp to gain additional playing experience. In his only professional football game, Kupp completed 3-of-7 attempts for 23 yards in the fourth quarter of the Cardinals' 34-0 loss to the Washington Redskins in week 3. On November 6, 1991, he was released to make room for quarterback Chris Chandler.
Dallas Cowboys
On November 7, 1991, he was claimed off waivers by the a Dallas Cowboys. After starter Troy Aikman suffered a knee injury in the twelfth game against the Washington Redskins, Kupp ascended from third-string to backup quarterback behind Steve Beuerlein. In 1992, he was one of three Cowboys' players to be allocated to the World League of American Football. He spent the first six weeks of the season with the San Antonio Riders, having scant action, before being acquired by the Montreal Machine, where he spent the remainder of the season as a backup. He made 11-of-27 completions for 138 yards, one touchdown and 4 interceptions. He was released by the Cowboys on August 31.
