We're nearing the conclusion of our series looking at two departing stars players from each Big Ten team whose shoes need to be filled this spring. Today we focus the lens on Northwestern, which started spring drills over the weekend. We already know that Kain Colter is the top choice to replace the large void left by quarterback Dan Persa, so we'll take a look at two other spots.

BIG SHOES TO FILL: Jeremy Ebert, WR

Why: Ebert was the Wildcats' leading receiver and one of the best in the Big Ten each of the past two seasons. He caught 75 passes for 1,060 yards and 11 touchdowns in 2011.

Replacement candidates: Christian Jones (6-3, 225, Soph.); Demetrius Fields (6-0, 210, Sr.); Tony Jones (6-0, 185, Soph); Rashad Lawrence (6-2, 185, Jr.); Kyle Prater (6-5, 215, Soph-Tr).

The skinny: The big X-factor here is Prater, the USC transfer who is hoping to gain immediate eligibility for this season. He will enroll March 26 and will have to wait for an NCAA ruling this summer. Christian Jones played in all 13 games last year as a true freshman, catching 16 passes for 195 yards. He's got the physical tools to be a No. 1 receiver. Fields had a career-best seven catches in the Meineke Car Care Bowl of Texas, perhaps signaling he's ready to take off. Tony Jones sat out last year because of injury but has a lot of speed. Northwestern has a lot of depth here, but can anyone produce at a consistently high level like Ebert?

BIG SHOES TO FILL: Brian Peters, S

Why: Peters was one of the leaders of the Wildcats' defense, a three-year starter who had 92 tackles and five interceptions last season. He was a first-team All-Big Ten selection by the media.

Replacement candidates: Hunter Bates (5-10, 180, Sr.); Jared Carpenter (6-0, 205, Sr.); Davion Fleming (5-10, 200, Jr.); Matt Carpenter (6-2, 200, R-Fr.); Jimmy Hall (6-2, 205, Soph.); Terrance Brown, (6-1, 195, incoming freshman); Traveon Henry (6-1, 200, incoming freshman); Joseph Jones (6-1, 200, incoming freshman).

The skinny: Bates has learned as Peters' backup and should be ready to challenge for a starting spot this spring, though he struggled at times in 2011. Jared Carpenter served as the backup at the other safety spot, which will be manned by sophomore Ibraheim Campbell, but Carpenter is injured and won't go through spring drills. Fleming and Hall are promising athletes who just need more experience. Defensive back in general is a concern for the Wildcats this spring after a subpar 2011 on pass defense and the loss of both Peters and top cornerback Jordan Mabin. Several young players could earn playing time with strong performances in practice.