With only four weeks to go, League One's promotion and relegation candidates are finally starting to narrow down.

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A couple of upsets at the top were combined with teams at the bottom confirming that their good form is no fluke at exactly the right time.

Unpredictability leads to uncertainty, and clubs who felt safe from relegation or confident on promotion just a couple of weeks ago are now crowded with doubt.

Here are the main five talking points of this weekend's action......

1. Crewe finally relegated

We talk about the league being unpredictable but Crewe's relegation had been a long time coming.

Having been in the bottom two positions of the league since late August, Steve Davis' men finally confirmed their League Two status next season after a 3-0 defeat at Port Vale.

Problems at Gresty Road have been ongoing all season on all levels of the club, from the board of directors through the pitch and right down to the academy.

Crewe's last-day heroics from the last couple of seasons will not be replicated this season and the only thing the Railwaymen will be looking forward to is playing in a division where the pressure of relegation won't be there from day 1.

2. Burton slip up once again. Automatic promotion in doubt?

If there's a time where you cannot afford to start stringing a run of bad results, that's in the months of March and April.

Still, Brian Clough's men are set on making life hard for themselves to achieve automatic promotion, after being in the top two places for most of the season with the odd and brief hiccup in-between.

The Brewers fell to a 1-0 defeat to Scunthorpe at Glanford Park courtesy of a Neal Bishop goal on the hour.

The worrying part is that they have only scored one goal in the last four matches, last week's stoppage time equaliser against Bury, and that they've drawn two and lost two in that span.

The fixture list provides little comfort, as Barnsley, Wigan and Gillingham will be the next visitors to the Pirelli Stadium with a tricky visit to in-form Colchester in between.

With Bradford City racking up the wins behind them, they are just six points away, six points that, at this rate, could disappear very soon.

3. Oldham march on, Blackpool drown, Colchester's salvation miracle on the cards?

The League One relegation battle is hotting up and there seems to be two or three teams that are hitting form at the right time. One of those teams is Oldham Athletic, who with yesterday 's surprise 1-0 win over high-flyers (or former high-flyers) Walsall, have put a bit of daylight between them and the relegation zone.

Curtis Main's second-half striker made it three wins on the bounce for John Sheridan's men and four clean sheets in a row.

With two games in hand over Blackpool, who sit in the last relegation spot, it would be relatively safe to say that they will be securing their League One status soon.

As for Blackpool, their good run came to an end with a disappointing 1-0 defeat to Colchester courtesy of a Chris Porter goal on 60 minutes. Blackpool are the team with the most matches played (42) in the relegation zone, and have three away fixtures to look forward to in their last four matches.

A win yesterday would have put them in a similar position to Oldham's but relegation is now a strong reality since they no longer depend on themselves to reach safety. The U's, on the other hand, are certainly trying to make miracles happen and are now just 8 points from safety on a run of three wins in the last four. Stranger things have happened.

4. Unstoppable Wigan make it 20 in a row without defeat, set for promotion

It's going to take a lot to stop Wigan from obtaining the League One title this season, never mind not winning a match.

Will Grigg's 23rd goal of the season gave the Latics a 1-0 win over Coventry and the victory meant that Gary Caldwell's men are now 4 points ahead of Burton in second place and 10 ahead of Bradford in third.

Promotion could be achieved as soon as next week if they manage to win at lowly Doncaster and Bradford and Millwall fail to win.

If Burton also fail to win next weekend, with the aforementioned scenario, Wigan could seal the championship with a win when they visit the Pirelli Stadium just a few days later. In any case and whatever happens, it's a case of when and not if.

5. Midweek action crucial for Gillingham, Walsall and Barnsley's play-off hopes

After this weekend's poor results for all three teams, Tuesday's fixtures between Gillingham and Walsall and Barnsley and Oldham have gained a whole new level of importance.

Gillingham and Walsall are tied on 68 points for the last playoff spot, while Barnsley are lurking six points behind, ready to pick up any pieces.

Gillingham's goalless draw at Sheffield United and Barnsley's surprise home defeat to Chesterfield (1-2) leaves a lot of uncertainty as to who will make the playoffs. Some questions might be answered come 10 p.m. on Tuesday.

What are your thoughts on this week's match action? Let us know in the comments box below!