The 1-0 defeat at Nottingham Forest saw them fall to seventh, two points behind Ipswich in sixth and three behind West Ham, Sunderland and Crystal Palace.
A point for Sunderland against Norwich tomorrow night would put the Black Cats out of reach, while the Hammers have a superior goal difference to Latics.
So it's really either Palace or Ipswich who will need to crumble.
Ipswich are the more vulnerable. If they only draw at home to Cardiff while Latics win, a better goal difference would book Latics their place.
This is only the third time since the end of August that Latics have fallen off the play-off pace.
Jewell said: "We're sick as this is the first time in quite a while we've been outside the top six.
"It's not been the best of weekends but now we must dust ourselves off, try to beat West Ham and see what happens then. We have still got a chance and there might yet be another twist in the tale yet – who knows?
"Whatever happens we have come a long way in a short space of time, and even to be in with a chance of getting into the play-offs and challenging for the Premiership is a credit to the players."
Sunday's fixtures, which all kick-off at 1pm, also see Sunderland at Burnley and Palace travel to Coventry.
Sheffield United and Reading, who are level on 70 points with Latics but behind on goal difference, are at Preston and Watford respectively.
Jewell felt Latics deserved something at Forest, only for their finishing to let them down. After David Johnson bundled the hosts ahead after 58 minutes, Nathan Ellington rattled the woodwork while Gary Teale had two good scoring opportunities.
Jewell said: "You can never question our effort but the final pass and final shot on goal wasn't as good as it should have been.
"It was a bit similar to last week against Sunderland.
"I thought we were the better side, had some great situations, but didn't make them pay.
"We haven't been good enough in the final third in the big games recently.
"Thinking back to Norwich, Sunderland and Saturday's game, we haven't really produced where it matters.
"Certainly against Sunderland and Forest we had the majority of the ball but haven't done enough with it.
"When you step up a level in this game, you have to grow up fast and be a lot more clinical in front of goal.
"It's better coming to Nottingham Forest and playing in front of more than 29,000 fans than it is playing in front of just 4,000 somewhere else.
"We're in this game to play in front of big crowds week in, week out, so we have to do better in these big games.
"Where we end up finishing in the league after 46 games is where we'll deserve to finish.
"If we miss out on the play-offs, it won't be because we have been unlucky, it's because we haven't been quite good enough."
Jewell was pleased with the contribution of Gareth Farrelly to the midfield, the former Republic of Ireland international completing his first 90 minutes for Latics.
"Gareth gave us a calmness and I was pleased because it was his first full game for us," said Jewell.
"He didn't train with us on Friday because his wife had a baby, and he only joined up with us at the hotel late on Friday night."
Source: Wigan Evening Post.
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