Chinese Basketball Association
Gaines signed for the Xinjiang Flying Tigers in 2009 and played 10 games in the playoffs of the 2008–09 Chinese Basketball Association season, averaging 29.5 points and 10.4 rebounds in 37.3 minutes per game. He stayed with the team for the 2009–10 season and posted averages of 30.4 points and 10.7 rebounds in 39.4 minutes per game over 43 appearances. On February 26, 2010, Gaines recorded a career-high 47 points against the Qingdao Eagles. He ranked second in scoring with 30.4 points per game behind Andre Emmett for the 2009–10 season and was a first-team All-CBA selection.
In 2010 Gaines signed for the Qingdao Eagles for the 2010–11 CBA season. On December 15, 2010, Gaines scored 43 points (along with 16 rebounds) against the Beijing Ducks. At the end of the season he recorded averages of 33.2 points, 13.1 rebounds and 2.4 steals per game in 32 appearances: he was the league's top scorer, the 5th best rebounder and was again named in the All-CBA First Team.
In 2011 he moved to the Shanxi Brave Dragons to play the 2011–12 season. He earned his first and only All-Star selection in 2012, and played for the Northern All-Stars team. During the All-Star game he posted a game-high 10 rebounds along with 24 points. on February 28, 2012, Gaines had a 20–20 game, scoring 29 points and recording 23 rebounds against the Shanghai Sharks. He finished the season averaging 29.1 points (4th in the league) and 14.3 rebounds (3rd in the league), and was named Foreign Player of the Week 3 times (weeks 3, 8 and 11).
On January 2, 2013, in a game against the Zhejiang Golden Bulls, Gaines scored 60 points and posted 29 rebounds, both career-highs. In the same game Quincy Douby scored a CBA record 75 points. In the 2012–13 season he was named 3 times Foreign Player of the Week (weeks 1, 4 and 5), and made the All-CBA second team with averages of 31.5 points, 15.2 rebounds and 2.2 steals per game. In the 2013–14 season he was named Foreign Player of the Week on Week 2 and was the league rebounding leader with 14.1 rebounds per game. He repeated this feat in the following season, during which he averaged 16.4 rebounds per game playing for the Zhejiang Golden Bulls. In the 2015–16 season he was the 8th best rebounder in the league with an 11.7 per game average.