James Stone was a model of composure after playing 85 percent of the snaps against the Ravens last week.

The undrafted rookie from Tennessee played like a seasoned closer coming out of the bullpen.

But against Detroit this week, Stone will make his first start against the Lions’ vaunted defensive tackles Ndamukong Suh and Nick Fairley. He’ll be on the international hot seat in London.

Coach Mike Smith said Harland Gunn will back up Stone.

Stone held up against the Ravens. He gave up two hurries on 45 pass-blocking snaps for a sterling pass-blocking efficiency rating of 96.7 percent by Pro Football Focus.

Stone, 6-foot-3, 291 pounds, will become the third starting center this season. He follows Joe Hawley and Peter Konz, who both suffered season-ending knee injuries.

Stone played 45 games at Tennessee and started 39 times.

“Good arm length for the position — able to extend,” wrote draft analyst Nolan Nawrocki for NFL.com’s predraft analysis of Stone. “Functional agility — able to slide and cut off penetrators. Experienced four-year starter. Has played some guard. Quick to the second level. Is intelligent and sets protections. Durable.”

He received a seventh-round/undrafted grade by NFLDraftScout.com.

His weaknesses, according to Nawrocki, include: “Deficient core strength. Limited push and power. Stiff lower body. Inconsistent leverage and contact balance — overextends, falls off blocks and gets tossed aside. Not a finisher.”