In the 2008–09 season, he pitched 31 innings in 18 games (one start), compiling a 2–3 record with a 7.84 earned run average (ERA).

On December 7, 2015, the Mariners traded Elías and Carson Smith to the Boston Red Sox for Wade Miley and Jonathan Aro.

He made one additional appearance for Boston during the season, pitching two innings of one-run relief against the Arizona Diamondbacks on August 16.

Elías started the 2017 season on the disabled list, due to a muscle strain suffered in early March.

[16] Elías started the 2018 season with Triple-A Pawtucket,[17] where he appeared in four games in relief, pitching a total of 7+1⁄3 innings with a 1.23 ERA, 1–0 record, and one save.

On April 23, 2018, the Red Sox traded Elías to the Seattle Mariners in exchange for a player to be named later (PTNBL) or cash considerations.

[21] On June 1, 2018, Elías was called up from Tacoma to make his season debut against the Tampa Bay Rays, in which he tossed two scoreless innings in relief, earning the win.

[22] Throughout the season, Elías was typically used as a long reliever or spot starter, finishing 2018 with a 2.65 ERA, 154 ERA+, 3.08 FIP, and 2.13 strikeout-to-walk ratio in 23 appearances (51.0 IP), including 4 starts.

[26] On July 31, 2019, the Mariners traded Elías and Hunter Strickland to the Washington Nationals in exchange for Aaron Fletcher, Taylor Guilbeau, and Elvis Alvarado.

However, he was forced to leave the game and was placed on the 10-day injured list after he pulled his right hamstring running down the first-base line during an at-bat the following inning.

[29] The Nationals finished the 2019 year with a 93–69 record, clinching the wild card, and eventually won the World Series over the Astros.

[31] On March 16, it was announced that Elias had suffered a torn ulnar collateral ligament that required Tommy John surgery and cause him to miss the 2021 season.

[35] He made one relief appearance for the Mariners, allowing one earned run on one hit and two walks against the Toronto Blue Jays.

[41] On May 23, 2024, after suffering an oblique injury, Elías was deactivated by the Landers, with Keisho Shirakawa signed as a temporary replacement player.