On April 2, it was announced that Yi would miss the rest of the season with a knee injury. Having already missed eight games with other injuries, Yi played in only 66 (out of a possible 82) games in his rookie season, averaging 8.6 points on 42% shooting and 5.2 rebounds per game. One of Milwaukee’s assistant coaches, Brian James, later said that “the injuries he had bothered him more than people realized, and he couldn’t play through them.”

On June 26, 2008, Yi was traded along with Bobby Simmons to the New Jersey Nets for Richard Jefferson.[ The Nets team president Rod Thorn said that “we feel strongly he’s going to be a real good player”, and the team’s chief executive Brett Yormark said “it opens up a truly new fan base for us.” Yi said he didn’t expect to be traded, but that it was “an honor to join the Nets.”

Through his first 37 games with New Jersey, Yi averaged 10.5 points and 6.2 rebounds a game, while shooting 39% from behind the three-point line, which was well above his average from the previous season. But on January 9, 2009, Yi broke the little finger on his right hand, and was expected to miss four to six weeks. Thorn called it “lousy timing” because “he’d been playing well”, but Yi said “(I’ll) just take my time. I’ll come back.” In voting for the 2009 All-Star Game, Yi finished third in total votes for Eastern Conference forwards, ahead of players such as Paul Pierce and Chris Bosh, which raised allegations of Chinese fans voting for Yi only because of his nationality.

Yi’s first major international experience came at the FIBA Under-19 World Championships, where he averaged 18.9 points and 11.5 rebounds per game. He debuted with the senior national team in the 2004 Olympic Games and averaged 6 points and 6 rebounds a game at the 2006 FIBA World Championships. His performance impressed coaches on the Chinese national team as well as the coaches from other countries.

In 2008, Yi was once again selected to play for the national team in the Beijing Olympic Games. In China’s first two groups games, Yi scored only 9 and 4 points respectively, and China lost both their games against the USA and Spain. But in a win against Angola, he recorded a double-double, and in the Chinese’s second win against Germany, Yi had 9 points and 11 rebounds,and hit the crucial shot with 28 seconds left, to help China advance to the quarterfinals. However, Lithuania ended China’s run by beating them 94–68, as Yi scored 11 points.

Yi is not the first Chinese player to come under scrutiny, as former NBA player Wang Zhizhi has been listed as being born in both 1977 and 1979. In 2004, Yi was listed as being born in 1984 in China’s Four Nation Tournament, although Chinese officials said that it was probably a typographical error. Two years later, Fran Blinebury of The Houston Chronicle reported that Yi told Shane Battier he was 24 in an exhibition game before the 2006 FIBA World Championship, although the story was refuted by both Yi and Battier.

In 2006, a senior CBA official admitted that past youth squads had included players above the permitted age,]and Yi’s longtime American teammate in China, Jason Dixon, said to Chad Ford that Yi was “21 or 22…It’s pretty common over [in China] to change ages”. In 2007, a Chinese government registration site made public by hackers showed Yi’s date of birth as being in 1984, and in December 2008, a Chinese reporter discovered school registration forms that listed Yi as being born in 1984.
Yi is fluent in both Mandarin and his native tongue of Cantonese, and although his English has improved in America, Yi still conducts interviews through his interpreter, Walter Ho. He is currently under contract with Coca Cola and Yili (a Chinese dairy company) to endorse their products in China, and after a bidding war with Adidas, Nike signed Yi to a six-figure endorsement deal. He was ranked fourth on Forbes’ Chinese celebrities list in income and popularity in 2007. In 2008, Yi donated 100,000 yuan to support the Sichuan earthquake victims, and also participated in the 2008 Summer Olympics torch relay by carrying the torch during the Hainan leg of the relay.[61]