Detroit ? Free-agent center Ben Wallace is leaving the Detroit Pistons to sign with the Chicago Bulls, a person within the NBA said Monday.

The person, who spoke to The Associated Press on condition of anonymity because NBA free agents can’t officially sign contracts until July 12, said the Pistons offered Wallace a four-year contract worth about $50 million. That would make him the highest-paid player on the team next season with a salary of $11.5 million.

Messages were left Monday night for Wallace’s agent, Arn Tellem, and a call to Wallace’s home in suburban Detroit went unanswered. But Wallace told The Detroit News that he would sign a four-year deal with the Bulls.

“I appreciate everything Detroit did for me and my family,” he told the newspaper Monday night. “They gave me an opportunity to make a name for myself, and we had an opportunity to win a championship together.”

Wallace helped Detroit advance to four straight conference finals – the first team to do so since the Bulls of the early 1990s.

Detroit had wanted to keep its starting lineup together, and Joe Dumars, the Pistons’ president of basketball operations, said late last week that his top priority was to re-sign Wallace.

But Wallace said he was disappointed with the Pistons’ offer.

“We tried to work out a couple of deals,” he told the newspaper. “But there was nothing that Joe felt would work.”

Wallace, a four-time Defensive Player of the Year, could be a good fit for an up-and-coming Chicago team that needs help with rebounding and defense.

He was just what the Pistons needed when they acquired him and Chucky Atkins from Orlando before the 2000-01 season in a sign-and-trade deal for Grant Hill.

Wallace helped Detroit advance in the playoffs in 2002 – for the first time since 1991 – get to the conference finals in 2003, win a title in 2004 and reach the finals last year.

The Pistons won an NBA-high and franchise-record 64 games last season, then lost to the eventual champion Miami Heat in the Eastern Conference finals.

During the regular season this past year, he ranked fourth in the NBA in rebounding (11.3), ninth in blocks (2.2) and 10th in steals (1.78) – the only player among the top 10 in all three categories.

The undrafted free agent from Virginia Union became the fifth player in league history to have 100 blocks and 100 steals in six straight seasons, a list that includes several big-named standouts like Hakeem Olajuwon, Julius Erving, Sam Lacey and David Robinson.

Wallace, who turns 32 on Sept. 10, scored 7.3 points a game this past season and has not averaged double digits in any of his 10 years in the league.

Since beginning in his career with the Washington Wizards, he has averaged 6.6 points and made 42 percent of his free throws.

The Pistons center, affectionately known as “Big Ben” by his fans, became the first player to win the Defensive Player of the Year award four times in a five-year span.