The Giants’ new-look defensive tackle unit will be without one of its holdovers.

Veteran starter Roy Robertson-Harris tore his Achilles during Thursday’s practice in what is a season-ending injury, The Post’s Ryan Dunleavy confirmed.

The Giants signed the 32-year-old to a two-year, $9 million deal last offseason, and he started all 17 games for the team, tallying 35 combined tackles.

This offseason has featured big changes for the Giants among their interior defensive tackle positions, with longtime standout Dexter Lawrence being traded to the Bengals for a first-round pick.

They ultimately used that pick — No. 10 overall — to select Miami offensive tackle Francis Mauigoa.

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The Giants then signed DJ Reader to a two-year, $12.25 million contract this offseason to be a starter.

The 10-year veteran is more of a run stopper than a pass rusher, having tallied just 12 ¹/₂ career sacks.

Big Blue also signed veterans Shelby Harris and Leki Fotu, with Harris expected to fill more of a role than Fotu under new defensive coordinator Dennard Wilson.

Harris has appeared in 146 career games with 89 starts, while Fotu — an ex-Jet — has played in just 66 games with 26 starts spanning six starts.

This injury also puts a greater emphasis on the development of 2025 third-round pick Darius Alexander after an inconsistent rookie season.

Alexander totaled 3 ¹/₂ sacks across 16 games last season, and the Giants will need him to complement their veteran additions in the quest to replace Lawrence’s production.

The Giants also added some depth in the draft when they selected Auburn’s Bobby Jamison-Travis.

Robertson-Harris had been readying for his 10th season in the league, having previously spent time with the Bears (2017-20), Jaguars (2021-24) and Seahawks (2024) before joining the Giants.

He has notched 19 career sacks across 134 games with 79 starts.