Upshall played with the Fort McMurray Oil Barons of the AJHL in 1999-2000 as a sixteen-year-old. In 52 games, Upshall had 26 goals and 52 points, helping the Oil Barons to the Royal Bank Cup. In five games at the Royal Bank Cup, Upshall had two goals and six points, helping the Oil Barons to the championship.
Upshall joined the Kamloops Blazers of the WHL in 2000–01. Upshall had a memorable rookie season, scoring 42 goals and 87 points in 70 games, helping Kamloops to the playoffs. In four playoff games, Upshall had two assists. After the season, he was named to the WHL All-Rookie Team, the CHL All-Rookie Team, and won the Jim Piggott Memorial Trophy as Rookie of the Year in the WHL, as well as the CHL Rookie of the Year.
Upshall had another very solid season with the Blazers in 2001–02, as he had 32 goals and 83 points in 61 games, followed by a goal and three points in four playoff games. Upshall also played for Canada at the 2002 World Junior Hockey Championship, where he had three goals and six points in seven games, helping the Canadians to the silver medal. After beginning the 2002–03 season with the Nashville Predators, Upshall was sent back to Kamloops on November 7, 2002. He then scored 25 goals and 56 points in 42 games with the Blazers. In six playoff games, Upshall had two assists. Upshall once again won a silver medal with Canada at the 2003 World Junior Hockey Championship. In six games, Upshall had four goals and five points.
Upshall appeared in eight games with the Nashville Predators in 2002–03, where he scored a goal. He was then sent back his junior hockey team, the Kamloops Blazers. After his junior season was over, the Predators assigned Upshall to the Milwaukee Admirals of the AHL, where in two games, he had a goal, followed by going pointless in six playoff games.
In 2003-04, Upshall had an injury plagued season, appearing in 31 games with the Admirals, scoring 13 goals and 24 points. Upshall also had a brief stint with the Predators in the NHL, where he had an assist in seven games. Back with Milwaukee for the playoffs, Upshall had three goals in eight games, as the Admirals won the 2004 Calder Cup. Upshall spent the entire 2004–05 with the Admirals, as Upshall had 19 goals and 46 points in 62 games, followed by two goals and four points in five playoff games.