The starting running back spot is still up for grabs between, from left to right, Roy Helu, Evan Royster and Tim Hightower. (John McDonnell/The Washington Post)

For some Washington Redskins, Saturday’s matchup against the visiting Indianapolis Colts and Wednesday’s preseason finale against the Tampa Bay Buccaneers represent the most important games of their careers — two last shots at the team’s roster.

For others, it’s a chance to solidify their standing in the minds of coaches, and for others still, an opportunity to continue jockeying for position on the depth chart.

But for the most part, the starting jobs have been filled.

On defense, the entire front seven and the two cornerbacks return from last season. And newcomer safeties Brandon Meriweather and Madieu Williams have held down the first-team duties since spring practices, though Meriweather is injured and may not be able to start the Sept. 9 season opener against the New Orleans Saints.

Questions continue, however, about two crucial offensive positions: Who will start at running back, and who will line up at the wide receiver spot opposite Pierre Garcon? On special teams, Graham Gano and Neil Rackers continue to battle for the place-kicking duties.

“We’re evaluating those guys every practice,” Shanahan said of the players at various contested positions. “We get two more games to evaluate them. . . a lot of playing time the second half from Indy and obviously most of the fourth game. So, those games are very important to a lot of those players.”

In the running back competition, the three backs who started last season have been coping with injuries. Until this week, second-year pro Evan Royster was the only healthy veteran, with Tim Hightower recovering from a November ACL surgery and another second-year back, Roy Helu Jr., sidelined the past two weeks by tendinitis in both Achilles’ tendons.

But Royster has missed the last two days with inflammation in his right knee. In limited action, he has rushed for 41 yards on nine carries. Darkhorse rookie Alfred Morris has recorded 88 yards on 25 carries.

Now after nine months of rehab on the ACL he tore last October, Hightower is slated to play Saturday. But Helu and Royster will not. Morris also will play, but said he hasn’t been told how much, or what his role will be.

Shanahan said he has no idea who will win the starting job, but downplayed the situation when asked his level of concern.

“I really don’t worry about things I can’t control,” Shanahan said. “We’re just going to get these guys back as quick as we can, get them healed up. It’s nothing season-ending, only one or two games, we hope.”

The ‘Z’ receiver position will come down to second-year pro Leonard Hankerson or free agent addition Josh Morgan. Both have been productive in practice, and Hankerson has started the last two preseason games at the position, recording two catches for 23 yards. Morgan recorded four catches for 49 yards with the second unit in the preseason opener against Buffalo, then went without a catch the following week.

Both should make the 53-man roster, as will Garcon, and Santana Moss seems like a lock at slot receiver. But five young players – Anthony Armstrong, Terrence Austin, Brandon Banks, Dezmon Briscoe and Aldrick Robinson – are battling for the final one or two slots.

All besides Armstrong – who missed time with a right shoulder injury and played just one snap in last week’s preseason game – have made plays. Against Chicago, Banks returned a punt 91 yards for a touchdown, Robinson had six catches for 104 yards and a touchdown, Briscoe had three catches for 51 yards and a touchdown, and Austin had a catch for 11 yards, while averaging 25.5 yards on two kickoff returns.

“The offense is running great right now,” Armstrong said. “You’ve just got to be able to fit in when you get your opportunity.”

The situation at cornerback closely resembles the contest at wide receiver. The top of the depth chart carries little intrigue, but the bottom is crowded and the picture is unclear.

DeAngelo Hall and Josh Wilson return as starters, but the third cornerback is often on the field for many snaps, requiring that player to be starter quality. Cedric Griffin – signed as a free agent in the offseason – and holdover Kevin Barnes are competing for that role. Griffin has received the bulk of the snaps with the first-team defense, but has struggled in two preseason outings, and coaches haven’t ruled out Barnes.

Barnes served as the team’s nickelback last season, but this year, Hall will move there and cover the opposing slot receiver, and the third corner will man the outside spot opposite Wilson. At 6-foot-1, 190 pounds, Barnes is more natural on the outside, Redskins coaches believe.

“Coach sees I’m always around the ball, always in position to make a play,” Barnes said. “But he just wants me to keep pushing my limits farther than I ever have.”

Second-year pro Brandyn Thompson, sixth-year veteran David Jones, a free agent addition, and rookie Richard Crawford also are fighting for inclusion at a position where the team likely will keep five and possibly six players.

“I would say it’s a more competitive situation this year,” said Thompson, who appeared in six games as a rookie and spent time on the team’s practice squad. “I would say that, at least in my mind, there’s not a dude in the room that can’t play. Obviously that makes things difficult for everybody. But you don’t worry about those things. You go out there, do your thing, and whatever happens, happens.”