The Detroit Lions have sunk a lot into the cornerback position the past two drafts and general manager Martin Mayhew is looking for that investment to start paying some dividends in 2014.

Two years ago, the Lions selected Bill Bentley in the third round, then added two rangier projects in Chris Greenwood and Jonte Green on the third day of the draft. Last year, the team snagged speedy Darius Slay at the top of the second round, the earliest the team had rolled the dice on a corner since 1998.

All four have struggled to varying degrees while adjusting to the NFL, but Mayhew is pleased with the upward trajectory of each player.

"Those guys are still improving if you look at how they played as rookies and how they played last year, there's improvement there," Mayhew said. "We want to see continued improvement from that group."

This isn't a case of a general manager propping up his players during the offseason. There was noticeable improvement from each corner, led by Bentley.

Starting the season as the team's primary nickelback, Bentley struggled out the gate. He surrender an abundance of receptions while drawing some backbreaking penalties in the first quarter of the season.

But as he settled into his role down the stretch, he was one of the team's more consistent defensive backs in coverage.

Slay also began the season as a starter, but was benched in favor of 11-year veteran Rashean Mathis, who had been signed off the street during training camp.

Taking the benching in stride, Slay embraced the opportunity to learn from Mathis. When the rookie got another chance, against the Packers late in the season, he delivered a stellar performance that included two pass breakups in the blowout victory.

Because of mounting injuries, Green and Greenwood both found their way into the lineup late in the season. The pair looked comfortable, especially Greenwood, the small school project who was seeing his first professional action nearly two years after being drafted out of tiny Albion College.

Given the way the four closed out last season, the bar has been raised.

"They all have experience now and this is a good year for all those guys to step up," Mayhew said. "Those guys aren't rookies anymore. They are second-and-third year players and we have high expectations for those group of guys."

-- Download the Detroit Lions MLive app for iPhone and Android

-- Follow Justin Rogers on Twitter

-- Like MLive's Detroit Lions Facebook page