FOXBOROUGH, Mass. -- Coach Bill Belichick said Tuesday that the New England Patriots liked quarterback Jimmy Garoppolo but traded him to the San Francisco 49ers because a complex situation had to be resolved eventually.

"We probably had, in my opinion, the best quarterback situation in the league for the last 2½ years, [but] it's just not sustainable given the way things are set up," Belichick said.

Describing it as "some form of decision that has been looming for the last couple of years," Belichick made it clear that the team's preference was to keep Garoppolo.

"It's definitely not something we wanted to walk away from," he said. "I felt like we rode it out as long as we could. Over a period of time, we explored every option possible to try to sustain it. But at this point, felt like we had to make a decision.

"It's a very complex situation on multiple levels. This is really the last window that we had [the trade deadline is Tuesday at 4 p.m. ET], and we did what we felt was best for the team."

Garoppolo, who turns 26 on Thursday, was selected in the second round of the 2014 draft (No. 62 overall). He was scheduled for unrestricted free agency after the season, and the two sides apparently could not reach agreement on a new deal. The Patriots got a 2018 second-round pick for him.

The Patriots still have 40-year-old Tom Brady under contract through 2019. In early September, the Patriots traded No. 3 quarterback Jacoby Brissett to the Indianapolis Colts.

That leaves Brady as the lone quarterback on the roster, but Belichick said, "We'll address the quarterback position and try to put our team in the most competitive position possible."

He wouldn't address whom the team might add, but with former Patriots backup quarterback Brian Hoyer (2009-11) reportedly going to be released by the 49ers, the Patriots are expected to sign him to fill the No. 2 role.

As for Garoppolo, Belichick said: "I have a tremendous amount of respect for Jimmy. I couldn't ask for him to give us any more than he has given us. The 49ers are getting a good player, they are getting a good person, and they're getting a great teammate, and they are getting a good quarterback. And Jimmy is getting a good coach. His career is moving forward. He's a talented individual. He was a great person to coach. I met with him weekly. But as his career moves forward, we have to look at our team, both this year and beyond."

Niners general manager John Lynch has spoken about how the trade came together.

"We tried to do a deal this offseason. It didn't come to fruition," he said, according to the team's website. "It presented itself now. We felt like it was an opportunity we had to jump at."