Miami Dolphins cornerback Xavien Howard requested a trade just hours after reporting to training camp on Tuesday.
Howard released a statement on social media, saying he signed a five-year, $75.25m (£54.3m) extension in May 2019 "that I'll admit I didn't completely understand".
"I've played on that deal for two seasons and didn't complain, but everyone knows I completely outperformed that deal," Howard said.
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"I'm one of the best cornerbacks in the NFL, and the tape backs up that claim. Yet I'm the second-highest paid cornerback on my own team, and it's not even close."
Howard said he never asked for a new contract, adding: "We wanted to work things out with the Dolphins and brought solutions to the table - like guaranteeing more money - that we felt were win-wins for both sides.
"But the Dolphins refused everything we proposed. I don't feel valued or respected by the Dolphins.
"Just like they can take a business-first approach, so can I. That's why I want to make it clear I'm not happy and have requested a trade."
Howard accumulated $93,000 (£67,000) in fines after skipping Miami's mandatory minicamp last month.
The two-time Pro Bowl selection will have a base salary of $12.075m (£8.7m) in 2021. However, teammate Byron Jones will make more this season - $14m (£10m) - after signing a five-year, $82.5m (£59.5m) contract in March 2020.
Howard was shown fist-bumping wide receiver Jakeem Grant on a video posted by the Dolphins earlier on Tuesday.
Dolphins coach Brian Flores was rather vague when discussing Howard's return. "We're excited to work with X and all the players that are here," he said.
"Those conversations with X's rep, Chris (Grier, Dolphins general manager) and myself will be internal and confidential."
Howard, 28, led the NFL with 10 interceptions and 20 passes defended last season and added 51 tackles and one forced fumble in 16 games.
He has 191 tackles, 22 interceptions and two forced fumbles in 56 career games (55 starts) since being selected by Miami in the second round of the 2016 NFL Draft.