Stags ended Saturday's first leg at home with a 2-1 lead but also with several players struggling.
“There are a few knocks, so we will be assessing them,” said boss Nigel Clough.
“Matty Longstaff said he felt shattered on Saturday. It happens with footballers young or old. He just felt under par, so we'll see how he is.
“Stephen Quinn is doubtful. He's playing with this hip injury he has had for a few weeks and wasn't moving particularly well on Saturday.
“Then there is George Maris and Stephen McLaughlin too. We will check on them all.
“But midfield is an area where we have lots of options. Look at the bench on Saturday.
“Keiran Wallace came on and did very well again and then there is George Lapslie, Ryan Stirk and Ollie Clarke. We have some good midfielders challenging for places. It's an area you need that competition.”
Clough is hoping his most experienced stars will help the others through what will be a hugely testing night tomorrow.
“Anyone with previous experience of these circumstances is vital in spreading their knowledge in how to deal with it,” he said.
“It is good we have an experienced squad as we will need it on Wednesday night.
“We will need cool, heads, calm heads and a bit of composure. And above all, the same spirit and fight we have shown all season – and not to concede.
“The first 15 minutes of the game is going to be absolutely crucial. We like to take the game to teams home and away, so we will be trying to do the same on Wednesday.
“We expect them to throw everything at us in that first 15 minutes, but we will be trying to do some damage ourselves.
“Trying to get a goal will be absolutely vital for us.
“It's the same for any away game. It starts with a clean sheet intact. If we do that we're in the game.
“It would be a very risky way to go about it to say we're going to defend for 90 minutes. I don't think we're that sort of team.
“It could be a long night – up to two hours and possibly penalties. We have to be prepared for that. We have been practising penalties since the Forest Green game.”
Clough hopes that the incentive of a Wembley final will also be a big factor.
“We are trying to get promoted, but the incentive of getting to Wembley, which you have to do to achieve that, is a considerable one for the players - and for the supporters - who've never been there,” he said.
“The players know where we're going if they win and they know what they have to do. It's just whether we can do it on the night.
“When you are 90 minutes away from a trip to Wembley, it is a huge incentive and everyone can't wait.
“It is something we have to use as a motivation. I know it's the end of a long, hard season. But I think it's the teams and the players that really put that to one side.
“No one epitomises it more than Liverpool. They have won two cups on penalties. They have played more games than anybody yet they're still challenging on four fronts.
“Whether it goes to penalties on Wednesday or not, that's the sort of mental strength you need.
“There was only one 2-0 victory and that was Wycombe early on at home, and they were playing against 10 men which I think made a difference.
“Every other play-off game has been a draw or a one-goal deficit in it.
“When you're playing teams that have been up there all season it's going to be closely contested games.
“Nerves kick in, everyone is a bit edgy. It is very difficult for teams to play their normal game in those circumstances.”
Clough was pleased to sign off at home with the first leg win.
“It was lovely to finish the home season with a win – that's 14 out of 16, which is two thirds of the season. It's an incredible record really. Now we've got to do something on the road,” he said.
“Northampton have to come out and try to get a goal. We don't have to, but with the way we play we will be trying to cause them problems.
“But I think it's going to be how we defend more than anything. You can't afford to switch off. We will have to defend as if our lives depend on it and you wouldn't expect anything less in this situation.
“It will give them a boost bringing their first choice goalkeeper back in.”
Having a first leg lead is new territory for the Stags' management team.
“In our two previous experiences of the play-offs we were level after the first leg at Burton and losing after a home tie at Sheffield United,” said Clough.
“We've never gone into a second leg with a lead. So that feels a little bit different and nicer. It's something to hang onto.”
Stags have sold out of their away tickets allocation of almost 1,500 and Clough added: “I think we'd be taking the whole stadium with us if we could.
“We had about 6,000 making the noise of 16,000 the other night. I know they will make an awful lot of noise again.”