The Mariners designated Bradley for assignment, giving them 10 days to trade, release or send him to the minors. He was making $13 million this season.
"The situation with Milton is that we determined he's not part of our future and not part of our present," Mariners general manager Jack Zduriencik said.
The 33-year-old Bradley hit .218 with two homers and 13 RBIs in 28 games. He was suspended for one game last week for bumping an umpire, ejected Friday for arguing a called third strike and booed by home fans over the weekend for the perception he was dogging it on defense.
"It was not a particular incident," Zduriencik said. "It's just an issue with our evaluations of where we are and where we are going, and our estimates were that he did not fit. That's why the decision was made."
Asked if Bradley had a negative impact on the clubhouse, Zduriencik said: "That's hard to say. I don't know that. I think it gets down more to what we're trying to accomplish and where we're headed."
Bradley is a career .271 hitter with 125 home runs since starting with Montreal in 2000. He has played for eight teams in the majors, including five clubs in the last five seasons.
The Mariners also cut utilityman Ryan Langerhans. He hit .171 with three home runs and six RBIs in 19 games.
Seattle called up outfielders Carlos Peguero and Mike Wilson from Triple-A Tacoma. Peguero played five games for the Mariners last month and Wilson will be making his big league debut.
Bradley got two hits Sunday in the Mariners' 10-inning loss to the Chicago White Sox. The defeat left Seattle at 16-19.
The former All-Star hit .205 with eight home runs and 29 RBIs in 73 games for the Mariners last year. He was sidelined for the season on Aug. 17 because of knee surgery.
Bradley missed time in midseason to undergo counseling after asking the club to help him deal with personal matters. He is finishing up a $30 million, three-year contract this season.
Zduriencik said he didn't necessarily regard the trade as a failure, especially since the Cubs released the high-priced Silva this spring.
"It was a situation where we looked the clubs' needs," he said. "It was a situation where we did not think Carlos was part of our future and obviously in Chicago [Milton] was not part of their future. We basically traded contract for contract and hoped it worked out for both clubs.
"We were in pursuit of bat and really hoped it worked out. At one time he was a very productive player," he added. "Do I think he can help a team? I think he can and hope he gets that opportunity."
As for Langerhans, "we liked his defense and the fact he plays multiple positions," Zduriencik said. "But at the end of the day we needed a little more production."
Peguero and Wilson will join the Mariners on Tuesday in Baltimore.
The 24-year-old Peguero was recalled by Seattle on April 19 when Justin Smoak was put on the bereavement list. He made three starts in left field and hit .182. Peguero was hitting .282 with four home runs and 13 RBIs at Tacoma.
The 27-year-old Wilson was the Mariners' second-round pick in the June 2001 draft. He was hitting .381 with four homers and 14 RBIs at Tacoma.
"Wilson has been here a long time. He has had the opportunity to leave because of different scenarios," Zduriencik said. "But he likes this organization. He has terrific power. He's had a nice start down there. He's a hard worker, he's paid his dues and he's got power from the right side. It's the right place at the right time for Michael."