After struggling with a left shoulder injury since training camp, defensive lineman Arik Armstead was finally placed on season-ending injured reserve on Tuesday.

Armstead is expected to undergo surgery to repair the shoulder, which forced him out of action in the past two 49ers' games. He appeared in the first six plays on Sunday against the New Orleans Saints but did not return to action.

Armstead did not appear in any games during the exhibition season after sustaining the injury during a practice.

Armstead, the 49ers’ first-round draft pick in 2015, is tied for the 49ers lead with 2.5 sacks. He appeared in eight games with four starts. He was credited with 21 tackles and one forced fumble.

The 49ers filled Armstread’s roster spot with the addition of defensive tackle Chris Jones, whom the Miami Dolphins waived on Monday.

Jones, 26, a sixth-round draft pick of the Houston Texans in 2013, has also spent time with Tampa Bay and New England. He posted nine sacks while appearing in 28 games in 2013 and ’14 with New England. Jones recorded a career-high six sacks in 2013.

Jones missed the entire 2015 season with a torn calf injury.