Six games into the season, the Patriots’ core has started to take shape, but there remain a handful of positions that are in a state of flux. Even as a key stretch of the schedule begins Sunday against the Steelers, there are positional battles being fought on both sides of the ball. Here are five different situations that bear watching over the next few weeks:

Inside/middle linebacker -- Brandon Spikes vs. Dane Fletcher: In our bye week breakdown of the linebackers, we took a closer look at the situations surrounding Spikes and Fletcher, and the fact that it’s not coincidental that with Spikes playing well as of late, it has started to eat into Fletcher’s playing time.

As Spikes has emerged, Fletcher’s snap percentage has decreased dramatically since the start of the season — according to Pro Football Focus, Fletcher played 45 percent of the snaps in the season-opener but has played just one snap the last two weeks. Meanwhile, after a slow start, Spikes has enjoyed a nice run over the last two games, missing just eight snaps over the last two weeks and making several big plays in New England’s win over Dallas. It remains to be seen how much of that is scheme and/or personnel related. (Fletcher has dealt with a thumb injury for the last few weeks, and was the only player missing from the start of practice on Tuesday.)

But even if he wasn’t dinged up, it’s clear that Spikes’ play of late may have moved him past Fletcher on the depth chart, nearly back to the spot where he was late last season before he was busted for violating the league’s substance abuse policy.

Safety -- James Ihedigbo vs. Josh Barrett/Sergio Brown: After the Patriots tried both Barrett and Brown at the safety spot at the start of the season with decidedly mixed results, they’ve turned to Ihedigbo, who has performed well since he moved into the starting lineup on a regular basis in Week 5 against the Jets. It’s clear the confidence level in Ihedigbo has increased dramatically since the start of the season -- after playing a combined 28 snaps over the first four weeks of the season, he’s only missed five snaps over the last two weeks combined. He’s not reinventing the position, but Ihedigbo has brought a consistency to the position opposite Patrick Chung over the last two weeks that’s been sorely lacking since the departure of James Sanders.

Meanwhile, Barrett and Brown have slipped rather precipitously since the start of the season, with the apparent turning point for the both of them coming in the loss to the Bills in Week 3. Both struggled against the run, and Barrett missed a bad tackle late on Buffalo running back Fred Jackson. (Since that loss to the Bills -- a stretch of three games -- Barrett has played a total of 17 snaps, while Brown has seen the field for 39 snaps.) To be fair, Barrett, who received the bulk of the snaps at the safety spot through the first three-plus weeks, has been battling a thumb and hamstring injury over the last month. But as was the case with Spikes and Fletcher, you certainly get the feeling that even without injury, Ihedigbo would have surpassed Barrett and Brown on the depth chart sooner rather than later.

Running back -- Stevan Ridley vs. Danny Woodhead: This isn’t so much a current depth chart battle like the first two, but two running backs who are fighting for reps in an increasingly competitive backfield that figures to be even more complicated with the possible return of veteran Kevin Faulk (not to mention the possibility of rookie Shane Vereen getting healthy at some point).

While Woodhead remains a fan favorite for what he did last season, there’s no denying that Ridley has cut into Woodhead’s production this season. In his first six games with the Patriots last season, Woodhead had 45 carries for 232 yards and two touchdowns, to go along with 16 receptions for 174 yards and one touchdown. This year through six games, Woodhead has 30 carries for 122 yards and eight carries for 63 yards. Meanwhile, Ridley has 28 carries for 180 yards and a pair of catches for 11 yards has gotten almost as many total touches as Woodhead has (38-30). No one is denying the fact that BenJarvus Green-Ellis remains the closest thing the Patriots have to a feature back, but after that, the battle for reps figures to get even more difficult as the season continues.

Julian Edelman -- Returner vs. Receiver: After he sparked comparisons to Wes Welker with a 37-catch rookie season, Edelman stumbled a bit last year with just seven catches, thanks in large part to the fact that he was unable to stay healthy. This season, he’s been utilized even less in the passing game than he was in 2010 -- he’s only been targeted six times through six games, and has been rendered a nonfactor as a receiver. Instead, he’s caught on as the regular punt and kick return man for the Patriots. With Edelman in the regular role, New England is ninth in the league in punt returns and 17th in the league in kick returns. Unless something drastic happens, Edelman should continue to be regarded as a returner first and receiver second.