ORCHARD PARK, N.Y. — The Buffalo Bills acquired three-time Pro Bowl defensive tackle Marcus Stroud in a trade with Jacksonville today in Buffalo's latest and most significant move to revamp its porous defense.

In exchange, the Bills gave up an undisclosed number of draft picks. FoxSports.com is reporting they will be a third- and fifth-round selection in this year's draft.

Stroud, listed at 6-foot-6 and 310 pounds, immediately solidifies a defensive line that also features pass-rushing end Aaron Schobel. And the seven-year veteran improves a defense that finished 31st in the NFL in yards allowed last season.

The move was completed after the Bills began revamping their defense on Friday, the first day of NFL free agency. That's when Buffalo signed linebacker Kawika Mitchell to a five-year deal and released veteran defensive tackle Larry Tripplett.

In another move today, the Bills signed former Minnesota defensive tackle Spencer Johnson to a five-year contract.

"It's certainly been an exhilarating 36 hours," Bills chief operating officer Russ Brandon said, introducing both Stroud and Spencer at a press conference. "We're certainly excited about what's transpired. ... We feel this is a significant day in Buffalo Bills history."

The Bills are coming off their second consecutive 7-9 season and have missed the playoffs for eight straight years — the longest drought in franchise history.

Stroud is scheduled to make $16.5 million in base salary over the final three years of his contract. He had the Jaguars' permission to seek a trade and arrived in Buffalo on Friday to meet with team executives and take a physical.

It's not clear whether Stroud's contract will be restructured as part of the deal.

Stroud is coming off a troubled season in which he finished on injured reserve. He missed the final three games after re-injuring his surgically repaired right ankle, an injury that hobbled him at the end of the 2006 season.

Stroud also served a four-game NFL suspension for violating the league's steroids and related substances policy. The player acknowledged he took supplements to help recover from the ankle operation.

"That's all last year, it's already in the past," Stroud said. "I want to show the guys I've got a lot left in the tank."

At his best, Stroud is the type of dominating presence the Bills could use to shore up the middle of their defense, which struggled against the run and had difficulty applying pressure.

Jacksonville's 2001 first-round draft pick out of Georgia, Stroud played an integral role in helping the Jaguars defense become one of the stingiest — especially against the run — over the past few years. Stroud had three sacks last season and 22 overall in 100 games.

Johnson's signing was overshadowed by Stroud's arrival.

Listed at 6-foot-3 and 286 pounds, Johnson has spent the past four seasons with the Vikings. He played in all 16 games this past season, finishing with 24 tackles and three sacks. In 49 career NFL games, Johnson has 108 tackles and four sacks.

The Bills might not be done adding players, yet.

Free-agent receiver Bryant Johnson and tight end Ben Troupe are both scheduled to visit with the Bills tomorrow, according to their agent, Joel Segal.

Buffalo is looking to upgrade both positions, and the 6-foot-3 Johnson is regarded as the type of tall and fast receiver the Bills hope to land to take pressure off Lee Evans.

Troupe played sparingly for Tennessee in 2007, catching only five balls for 47 yards. He had a career-high 55 receptions in 2005 for the Titans.

The Bills have just one veteran tight end, Robert Royal, on their roster.