WASHINGTON -- Sean Doolittle has formed a strong connection with the Nationals community over the past four years. Before he enters free agency this offseason, he tweeted a thank you to Nats fans on Thursday night reflecting on his time in Washington.

"I know the 2020 season didn't go to the way we all hoped it would, but I wanted to say thank you for all the love and support you have given me during my time in DC," Doolittle began the message.

Washington acquired Doolittle in a trade with Oakland in July 2017. From there, the left-handed reliever pitched to a 10-10 record with 75 saves and a 3.03 ERA over 142 2/3 innings. He led the National League in games finished (55) in 2019. During the Nats World Series run last year, Doolittle posted a 1.74 ERA with two saves across 10 1/3 frames in nine playoff games.

This season, though, was full of obstacles. Doolittle, 34, struggled in late innings, and his ERA jumped to 15.00 before he was placed on the 10-day IL with right knee fatigue in mid-August. He was candid about the struggles he had to overcome at the alternate training site in Fredericksburg, Va., and he suffered a season-ending right oblique strain on Sept. 10 as he was re-establishing a rhythm on the mound.

“This year was especially challenging but, with the support of my teammates and our staff, I learned a lot about myself as a player and as a person that will help me for the rest of my career,” Doolittle wrote. “As difficult as it was, I'm grateful for the experience (bumpy roads, right?).”

Doolittle and his wife, Eireann Dolan, have been involved in numerous areas of the Washington community since joining the Nationals. He was named a finalist for the 2020 Roberto Clemente Award, which recognizes the game’s philanthropic and humanitarian players, and was voted a three-time "Good Guy" Award winner by members of the local media.

"DC will always hold a special place in our hearts," Doolittle wrote. "We got married here in 2017. We immersed ourselves in the District. We fell in love with the city."

As Doolittle faces free agency for the first time in his career, he plans to spend the offseason training at Driveline Baseball, a data-driven training center, in Seattle. He said on Sunday his goal is to “prove to teams that I’m healthy, that the version of me that came off the IL and started pitching better is who they might see in 2021.”

"I don't know where this game will take us next, but I'm so grateful for the time I had with the Nationals organization here in Washington," Doolittle concluded his message. "It was a privilege to wear the curly W and play for you at Nats Park. Baseball is a small world, so I look forward to our paths crossing again soon. Thank you for everything."