Most NFL general managers will tell you that they want to build the core of their roster through the draft, developing young talent for years to come, while free agency is used more to fill gaps and add veteran pieces here and there.

But the Giants have added some key players over the years via the free agent market, many of whom helped the team either reach or win the Super Bowl.

Here are some of the best free agent pickups in Giants history…

RT Kareem McKenzie, 2005

Originally a third-round pick of the Jets in 2001, McKenzie signed a seven-year deal with the Giants in 2005 and locked down the right tackle spot on a pair of Super Bowl teams. A force in the running game, McKenzie was also a beacon of durability, missing only seven regular season games in his seven years in a Giants uniform.

C Shaun O’Hara, 2004

When the Giants traded for Eli Manning during the 2004 draft, the team knew it would need to build around its new, young face of the franchise. And what better way to help a rookie QB learn the ropes than pairing him with a reliable, veteran center?

The Giants signed O’Hara -- who had been an undrafted free agent signing of the Cleveland Brown -- in 2004, and he immediately took over as the team’s starting center, anchoring an offensive line that was in need of a new look. O’Hara earned three Pro Bowl nods with the Giants and helped the team win Super Bowl XLII. He was released in 2011, and officially retired as a Giant in 2012.

WR Plaxico Burress, 2005

Burress was electric as a Giant and was a big reason why they reached the Super Bowl in 2007, as he pulled in 70 passes for 1,025 and 12 touchdowns that season. But Burress’ tenure will always have a footnote of “what could have been?”

Burress had a contract dispute ahead of the 2008 season, and was suspended for one game later that year for not showing up to work. Then, in November, Burress infamously shot himself in the thigh at a New York City nightclub, leading to prison time and the end of his tenure with the Giants.

Still, in parts of four seasons, Burress hauled in 244 passes for 3,681 yards and 33 regular season touchdowns, while also catching the game-winning TD pass from Manning in Super Bowl XLII

QB Kerry Collins, 1999

Collins came out of Penn State with plenty of hype and was drafted fifth overall by the Carolina Panthers in 1995. But his time with the Panthers was pretty uninspiring, as he compiled a 22-20 record as a starter and completed just 51.8 percent of his passes with more interceptions (54) than touchdowns (47).

After being traded to the New Orleans Saints in 1998, the Giants signed him ahead of the 1999 season to be Kent Graham’s backup, but Collins took over the starting job in Week 11 and never turned back. He led the Giants to a 12-4 record in 2000 and helped take the team to the Super Bowl, only to be blown out by the Baltimore Ravens.

But Collins ended up having a successful five-year tenure in New York, throwing 81 touchdowns and leading the Giants to a pair of double-digit-win seasons.

LB Antonio Pierce, 2005

Much like O’Hara, Pierce worked his way up from undrafted free agent to a starter, starting 16 games with Washington in 2004. The Giants signed him the following offseason, and he became a stalwart in the middle of their defense for the next five seasons.

Pierce became a captain of the Giants defense and earned his first career Pro Bowl nod in 2006, when he recorded a career-best 139 combined tackles. In total, Pierce played in 69 regular season games for the Giants, playing in at least 13 games every season as the team’s starting middle linebacker.

S Antrel Rolle, 2010

Rolle was a Top 10 pick of the Arizona Cardinals in 2005, starting out as a cornerback before moving to safety. After a Pro Bowl season in 2009, the Cardinals released Rolle in a salary-saving move, and the Giants swooped in and signed him to a five-year, $37 million deal that -- at the time -- made him the highest paid safety in NFL history.

Rolle played out that entire contract with the Giants and earned two Pro Bowl appearances and two Second-Team All-Pro selections. He had 14 regular season interceptions and five forced fumbles as a Giant, proving to be a valuable piece of the secondary and helping the team win Super Bowl XLVI.