Sprague began racing street stock cars at local short tracks, winning track championships at Thunderbird Raceway and Winston Raceway in Michigan. He moved to the NASCAR Winston Racing Series, competing in its North Carolina Late Model Division, and won the Big Ten Championship at Concord Motorsports Park along with more than 30 late model races before winning the NASCAR Winston Racing Series championship at the same track.
In 1989, Sprague finished first in the inaugural race of the NASCAR Sportsman Division at Charlotte Motor Speedway but was disqualified in post-race inspection, with the win awarded to Tim Bender.
Sprague made his Busch Series debut in 1989 at Charlotte Motor Speedway, driving the No. 78 Griffin Racing Chevrolet and finishing 41st after an early engine failure. He competed for Frank Cicci Racing in 1990, running nineteen races with a best finish of sixth at Orange County Speedway. In 1991, he drove a No. 48 Staff America-sponsored Oldsmobile and won his first career Busch Series pole at Charlotte. He secured a second-place finish at New River Valley Speedway in 1992.
Sprague signed with BACE Motorsports in 1993 for the No. 74 entry, posting four top-ten finishes before being released late in the year with nineteenth in the points standings. He returned to the Busch Series briefly in later years, including a race at Watkins Glen in 1998 and 1999, and won his first career Busch race at Nashville Superspeedway in 2002 while leading the standings for part of the season before finishing fifth.
Sprague joined the NASCAR Craftsman Truck Series in its inaugural 1995 season, initially with Griffin Racing and then switching to the No. 25 Budweiser-sponsored Chevrolet for Hendrick Motorsports. He ended the year with three fourth-place finishes and a pole at Phoenix. In 1996, with the No. 24 Quaker State truck for Hendrick, he won at Phoenix, then claimed back-to-back victories at Nazareth Speedway and The Milwaukee Mile. He accumulated five wins and two poles but lost the championship by 53 points.
In 1997, Sprague won at Phoenix, Nazareth, and Nashville Speedway USA to claim his first Craftsman Truck Series championship. Without Quaker State returning as his primary sponsor, he began 1998 unsponsored before winning The No Fear Challenge in his debut for GMAC, which then joined as full-time sponsor. He won five races and finished second in points.
Sprague claimed his second championship in 1999, winning three races to edge his nearest rival by eight points. He won three more times in 2000 but six DNFs pushed him to fifth in the standings. The 2001 season was his most dominant: with NetZero as his primary sponsor, he captured seven poles and four race victories to win his third and final Craftsman Truck Series title.
After 2001, Sprague moved back to the Busch Series with Hendrick Motorsports, driving the No. 24 NetZero Chevrolet. He won at Nashville Superspeedway and led the points during the season before finishing fifth. He also competed in the IROC series that year, finishing in the top ten in all four events.
Sprague attempted to establish himself in the Cup Series with Haas CNC Racing in 2002 and 2003, with his best result a fourteenth-place finish at the 2003 Daytona 500. He was released from the team after the Tropicana 400 in 2003.
He returned to the Truck Series with Xpress Motorsports and continued competing through 2008, winning at Texas Motor Speedway in 2005 and opening the 2007 season with a win at Daytona in the Chevy Silverado HD 250. His 2006 campaign produced two wins and a fifth-place points finish. He drove for Kevin Harvick Incorporated in 2008 before returning to Wyler Racing late in the season. Sprague stepped away from full-time competition after 2008 and was inactive through 2010 and into 2011.
Sprague's three Craftsman Truck Series championships placed him alongside the series' most accomplished competitors and helped establish the Truck Series as a legitimate and popular NASCAR division during its formative years in the late 1990s.