Since mid-August, the Lions have acquired three players who were first- or second-round draft picks in recent years. Each needed a fresh start.

If there’s a need, general manager Martin Mayhew is on the case. All three additions have come on defense which is certainly no surprise.

Cornerback Alphonso Smith, a second-round pick in 2009 (37th overall) came to Detroit in a trade that sent tight end Dan Gronkowski to the Broncos on Sept. 4.

Defensive end Lawrence Jackson, a former 2008 first-round pick by Seattle (28th overall, out of USC), arrived Aug. 18 after the Lions traded a sixth-round pick in 2011 to the Seahawks.

Just last week the Lions signed linebacker Bobby Carpenter, a first-round pick by Dallas in 2006 (18th overall out of Ohio State), who was cut by the Miami Dolphins on Tuesday.

In the offseason coach Jim Schwartz repeatedly said that the roster was not written in stone. That the Lions could still sign a player who would be a game-changer.

Will one of these three be the guy?

First, it’s too early to tell on Carpenter. His first practice with the Lions was Thursday. With the shortage at linebacker due to injuries, he could be thrown into action next Sunday against the Washington Redskins. He’s got experience inside and outside which made him more attractive because the Lions are short at both.

We’ll give Jackson an incomplete. He was slowed down from the get-go when he arrived with a hamstring injury. He’s seen some game action, but it’s too early to see what an impact he could make.

The winning grade so far goes to Alphonso Smith who played so well at nickel back that it was difficult to keep him off the field. He had an interception in three straight games and has started the last two games. Last year at Denver he played in 15 games with zero interceptions.

Schwartz likes him because he has a nose for the ball. While at Wake Forest he became the ACC’s all-time leader in career interceptions with 21. Some things don’t change, despite the move from college to the pros. (Perhaps it was the thin air in Denver or the system.)

Smith is looking more and more like a quite a pickup. Could he be a game-changer?

Absolutely.

(Follow me on Twitter @PaulaPasche.)