The San Francisco 49ers will reduce their 90-man roster to 75 players on Tuesday, making tonight’s game crucial for those on the bubble.

Players will have the chance to showcase their skills in a preseason tilt with the Minnesota Vikings at Candlestick Park at 5 p.m. on NBC. Here’s a look at a few of the position battles:

Quarterback

Colin Kaepernick and B.J. Daniels are safe. Struggling veterans Colt McCoy and Scott Tolzien are not, especially now that Eric Mangini-favorite Seneca Wallace is in town.

McCoy and Tolzien must be efficient and lead touchdown scoring drives to convince the coaching staff to keep them around. Wallace’s signing and versatile skill set are indicative of the type of quarterback the 49ers are looking for.

Running back

It’s probably just for a practice squad spot, but sophomore Jewell Hampton and rookie D.J. Harper are battling for it.

Hampton has leverage entering his second year with the team and proving he could handle the rock last week. Harper is versatile and a good pass protector, but a lost fumble against the Broncos doesn’t look good.

Wide receiver

Since last week’s game at Kansas City, A.J. Jenkins was dealt to the Chiefs for Jon Baldwin and Ricardo Lockette has been cut.

All eyes will be on Baldwin, who should make the team along with Anquan Boldin, Marlon Moore, Kyle Williams and Quinton Patton. Chuck Jacobs has all but earned a practice squad spot, meaning veterans Austin Collie, Lavelle Hawkins, Kassim Osgood, and Chad Hall are battling for a possible sixth receiver spot.

Tight end

Vernon Davis and Vance McDonald are locks, but last year’s No. 3 Garrett Celek could be on the way out with the ascent of multi-talented rookie MarQueis Gray, the converted college quarterback and wide receiver who is also a logical candidate to serve as an emergency in-game signal caller.

Nose tackle

Ian Williams has emerged as the starter throughout camp and preseason. Paying Glenn Dorsey $3 million to be a backup and rotational player doesn’t seem quite right.

Practice squad veteran Lamar Divens is next on the depth chart, but rookie Mike Purcell has looked good in both preseason games and can further his case Sunday night.

Linebackers

With four All Pro’s and five very good backups, the 49ers have the best linebacking corps in the league, bar none.

Keeping a tenth on the active roster may be a stretch, but Nate Stupar has been stellar this preseason as he battles practice squad veteran Joe Holland, 2012 seventh-rounder Cam Johnson, and rookie Travis Johnson for a job.

Specialists

Yes it’s true:The competition is even between Pro Bowl long snapper Brian Jennings and rookie challenger Kevin McDermott.

Math may also play a role here as Jennings is scheduled to make $940,000 this season while McDermott would earn $405,000 if he makes the roster.

All-Pro punter Andy Lee is safe, but rookie Colton Schmidt does make carrying three legs with kicker Phil Dawson an intriguing option, given his ability to seemingly win the team field position on every punt and kickoff.

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