Latics' assistant manager Chris Hutchings said: "They have both been training today. Nathan has got to make sure he keeps at it with his shoulder and works hard with the weights and if he does that he should not have too many problems.
"Lee came through a hard training session on Thursday and hopefully he should be fit as well.
"We just have to keep an eye on them to make sure they do not get any reaction from their injuries before Saturday."
Full-back Leighton Baines is expected to shake off the effects of a head injury, which saw him come off in last weekend's defeat at Queen's Park Rangers.
And with midfielder Alan Mahon likely to overcome a slight stomach strain, the injury storm clouds appear to be clearing.
The fitness of top-scorer Ellington, who has netted 11 times this season, and Scotland international midfielder McCulloch are major boost for Wigan.
Latics are looking to bounce back from two consecutive defeats which brought their unbeaten start to the Championship campaign to an end – and silence the doubters who have questioned their ability to go the distance.
Hutchings said: "We do not like losing and one or two people may start to question things, but it is all about how we bounce back from those
results.
"In the past we have bounced back with good results. On Saturday (at QPR) we were very unfortunate to lose the game, so we are not too worried.
"If we were not creating chances that would be a worry, but we are creating plenty of chances at the moment, just not taking them.
"We cannot rely on the strikers all the time, so it is up to one or two other people to step in and help them out."
The Leicester match heralds the start of an important period for Latics as they look to go into Christmas on a high note.
After tomorrow's match they travel to third-placed Reading the following weekend, before a derby with Preston North End at the JJB on December 4.
Fellow promotion hopefuls Ipswich Town and Derby County are also among their opponents in December.
Hutchings added: "All the games we have are tough. People expected us to beat Plymouth a fortnight ago, but they came to the JJB and gave us a beating and won 2-0.
"Again, on Saturday we got beaten and we felt we were very unfortunate, so on their day anyone can beat anyone in this division and we just have to make sure that does not happen to us against Leicester.
"People always say that you get to January and then you have some idea of what the table says.
"You take each game as it comes, we have been on a great unbeaten run and suddenly we lose two on the spin and people are questioning you – but we are top of the table and we are there for a reason.
"Teams will be coming here to knock us off the top and we have got to make sure we are strong enough to be in the position we are in and I am sure we will do."
Meanwhile, Leicester manager Craig Levein has been successful in his bid to bring in a goalkeeper after signing Arsenal number two Stuart Taylor on a one-month loan yesterday.
The 23-year-old goes straight into the squad for the JJB clash and challenges veteran Kevin Pressman for the gloves with first-choice stopper Ian Walker out for another two months with a knee injury.
Levein said: "I think everybody knows that we have been very thin on the ground as regards the goalkeeping position. Stuart will go straight into the squad for the Wigan game, but whether he starts that match is another thing."