In his Rookie season, Kevin was named the NBAs Rookie of the Year and selected as a member of NBA All-Rookie First-Team. That season he also received the NBA Rookie of the Month award five times and averaged 20.3 ppg, 4.3 rpg and 2.4 apg in 34.6 minutes per game. Kevin became just the third teenager to average more than 20 points per game. He scored a career-high 42 points and a career-high 13 rebounds on April 16, 2008 at Golden State at age 19 years 200 days. No player in the history of the NBA has scored as many points in a game at a younger age.
In his second season, Kevin averaged 25.3 points, 6.5 rebounds, and 2.8 assists per contest for the newly established Oklahoma City Thunder. On February 13, 2009, he captured the MVP award of the Rookie/Sophomore T-Mobile Challenge by scoring a team-high 46 points.
In his third season, Kevin earned his first All-NBA First Team selection after becoming the youngest player (21 years and 197 days) to lead the league in scoring (30.1 ppg). His 756 free throws made was the sixth highest single-season total in NBA history and the highest since Michael Jordan made 833 in the 1986-87 season, while his .900 percentage from the line ranked sixth overall. Kevin also recorded a streak of 25 points or more in 29 straight games, the second longest streak of scoring 25 points or more in league history. He capped his season by leading the Oklahoma City Thunder to the playoffs and earning NBA Western Conference Player of the Month honors for the month of April.