Most NFL coaching staffs consider training camp the primary battle ground for any open spots they might have in the starting lineup.  OTAs and mini-camps and other offseason activities are mainly aimed at getting players near peak physical condition and installing as much of the offensive and defensive systems as possible.

Still, there's no doubt that a player can make a solid impression during the spring and early summer, and even if there is no official depth chart at that time of the year, there are opportunities to advance.  Last year, for instance, rookie running back Doug Martin was so obviously impressive during the months that followed the 2012 draft that he essentially came into training camp as the leader on the depth chart.

With that in mind, there are a number of positions among the Bucs' starting 22 that, while not necessarily close to being decided, are perhaps gaining some clarity now during late May, heading into June.  These are essentially the main camp battles that we'll be watching once the team gathers in late July to get the 2013 campaign underway.

Just advancing from the 22 players who started the Bucs' season-ending win in Atlanta last year, there are likely to be around 10 different starters when the 2013 season begins in September.  Ronde Barber has retired, while Michael Bennett, Roy Miller and E.J. Biggers moved on via free agency, so that's three necessary new starters right there.  Injured starters Davin Joseph, Carl Nicks and Adrian Clayborn are expected to return to the front line, and the Joseph-Nicks guard combo on the O-Line should push Jeremy Zuttah back to his preferred position at center.  Prized secondary acquisitions Darrelle Revis and Dashon Goldson are nearly sure bets to start, as well.

Theoretically, of course, there could be up to 22 new starters in February.  Head Coach Greg Schiano stresses competition at every position, though there are clearly some spots where a change would be a big surprise.  It's like Schiano said a week ago regarding the quarterback position: "The truth is that I believe in competition, but also that Josh Freeman is our starting quarterback."

So here are the positions that are most likely to be up for serious competition during training camp this year…and, to some degree, right now during the offseason workout program:

- Strongside Linebacker

Quincy Black was the starter when the 2012 season started, but he suffered an injury that has still not allowed him back on the field, and he is no longer on the Bucs' roster.  Versatile veteran Adam Hayward, a long-time special teams captain, was the primary fill-in during the last six weeks of the season.

Hayward remains on hand, and is thus an obvious candidate.  Former New Orleans Saints Jonathan Casillas was signed early in free agency and has some starting experience in the NFL; he was clearly brought in to be an option for the SLB spot, even as he helps out on special teams and provides depth.  In addition, General Manager Mark Dominik has said that fourth-year player Dekoda Watson shouldn't be overlooked in this competition.  Watson is a phenomenal athlete with impressive speed, so he could conceivably add a pass-rushing element to the position if he wins the job.  Watson has always been in ridiculously good shape, but he apparently added some muscle weight during the offseason and thus might be even better holding up tight ends on the strong side.

Najee Goode, a fifth-round draft pick in 2012, could be a dark-horse candidate, as well.  Goode didn't see any real time on defense as a rookie but would now have the advantage of a year of learning the Bucs' system.

- Nose Tackle

That's Roy Miller's vacated spot, and the Bucs may have found a quick replacement in the draft, if they are right about how fourth-rounder Akeem Spence will fit in their defense.  The 6-1, 307-pound Spence was one of the strongest players in the draft, and he played several different DT techniques at the University of Illinois.  "Tilt-nose," what Miller played last year, wasn't one of those positions Spence played, but the Bucs believe he is perfect for it.

Spence won't be handed the job, however.  Veteran Gary Gibson, who was essentially the third man in the Bucs' DT rotation last year, could step up into a bigger role; he was a 16-game starter as recently as 2010 in St. Louis.  Similarly, Derek Landri, who signed with the Bucs as a free agent in late March, started 16 games in 2010 (for Carolina) as well as seven just last year in Philadelphia.  Both Gibson and Landri seem like solid, veteran options for the front line, at the least.

Less obvious candidates include Andre Neblett, just signed earlier this month after three seasons in Carolina.  Neblett started four games in 2011 and had 2.5 sacks that season.  Second-year man Matthew Masifilo came aboard at midseason last year so this will be his first training camp opportunity to prove that he should be in the mix.

• Right Cornerback/Nickel Back

Given the series of moves the Bucs made through the draft, the trade market and their own roster in
April, it's not hard to figure that the Darrelle Revis, Johnthan Banks and Eric Wright are the leading candidates to fill the top three cornerback spots.  That includes the starters on the left and the right and the primary nickel back, and there isn't a huge drop-off in the importance of those positions, as the extra DB in nickel packages plays a very high percentage of the team's snaps over the course of a season.

Revis, assuming he's ready to go at the beginning of the season, is the obvious answer at left cornerback.  Perhaps Wright will slide back in at right corner, where he started the first 10 games last season, and Banks will have a shot to be the nickel back.  Or, as some have already predicted, Banks will play on the outside and Wright will take over the job in the slot, for which he may be perfectly suited.

The Bucs also got plenty of opportunities to look at young corners last year – more than was planned, to be sure – so there could be some hope that Anthony Gaitor, Leonard Johnson and/or Danny Gorrer will be able to handle significant roles in 2013.  The team also seems high on 2013 undrafted free agent Deveron Carr out of Arizona State.

- Tight End

Luke Stocker actually started that 2012 season finale in Atlanta, but that was no surprise.  Stocker started 11 games last year, his second in the NFL, sometimes as the second man in a two-TE set, and sometimes alone in an obvious running set.  Dallas Clark was obviously considered the Bucs' "starting" tight end, even though he had four fewer starts than Stocker; Clark had 47 catches to Stocker's 16.

Buccaneer management believes in Stocker and thinks he could develop into a two-way starting tight end, helping with both his blocking and his pass-catching.  That emergence could happen this year.  Or, under-the-radar free agency acquisition Tom Crabtree could step up instead and become the primary option.  Crabtree earned a reputation as a very good blocker during three seasons in Green Bay, and when he had a chance to make plays in the passing game he did so quite well.

Those looking for a dark horse candidate at this spot might want to look at second-year man Danny Noble.  Noble was the biggest rookie surprise of last year's training camp, going from May tryout player to a spot on the 53-man roster.  Noble never really got a shot to prove himself during the regular season due to a season-ending injury, but he's healthy again and will have a shot to build on his early promise.