The 34-year-old will have a scan today to discover the full extent of the damage caused when he suffered a torn Achilles tendon in his right ankle after just six minutes of Saturday's 2-1 defeat at Barnet.
Woodman, who kept three clean sheets after replacing Jamie Young, will then have surgery within 48 hours to rule him out of action until next season.
Diamonds physiotherapist Simon Parsell revealed: "He will have a full scan today to see how much damage there is, whether the Achilles tendon is totally ruptured or just badly torn.
"He will also have to see a specialist in London and get an operation booked in by Wednesday. There is some urgency and we need to get on with it so the injury isn't even worse. But we can write him off now for the rest of the season.
"We went to Barnet General Hospital on Saturday night and saw a consultant. But it's a specialist job when you're dealing with a sportsman so we have just put Woody's leg in plaster for now to hold it in position until surgery."
Woodman's injury kicked off a dismal day for Diamonds as Barnet ended a run of 11 games without a win in Coca-Cola League Two.
Striker Drewe Broughton must serve a four-match ban for his second sending-off this season and left-back Peter Hawkins will also miss the FA Cup first-round tie away to Halifax Town on Sunday for his fifth booking.
Winger Marcus Kelly is also ruled out with a fracture in his right thumb.

FOR very different reasons Andy Woodman and Drewe Broughton could be lucky to ever play first-team football at Rushden & Diamonds again.
Our best wishes go out to goalkeeping coach Woodman who faces a scan today and surgery within the next 48 hours after suffering a torn Achilles tendon.
But there can be absolutely no sympathy for Broughton at all after a third red card in his past 15 league games.
While Woodman faces the rest of the season on the sidelines, perhaps it's also time to leave Broughton out of the squad due to his further disciplinary problems.
Broughton is well aware that the officials know all about his reputation, rightly or wrongly. Yet he still gets himself into trouble far too often.
There can be no excuses for any of his dismissals in a Diamonds shirt as he has deserved the punishments each time.
On his way down the tunnel at Underhill, he tried to explain to boss Barry Hunter that it was just a case of shirt-pulling with Barnet centre-half Ismail Yakubu. But actions spoke louder than words as the striker was told where to go!
Hunter later admitted: "I have got to be careful what I say now. But I thought he let everybody down.
"If I find out he has done what I think he has done I will then have to deal with him.
"We'll see what happens and address it. That's the end of it."
Hunter was understandably unhappy and Broughton can now expect to be fined quite heavily for his second sending-off already this season.
Whether that will also lead to Broughton's exit is more unlikely. But he can't have much of a first-team future now, particularly due to the arrival of Alun Armstrong plus the young talent ready to come up through the ranks.
Broughton faces a four-match ban for violent conduct with plenty of time to reflect on how he has let down the club.
Referee Ray Lee had been called over by his assistant over the off-the-ball incident as Broughton and Yakubu tangled chasing David Bell's crossfield pass. Shirts were being pulled but Broughton clearly waved his arm and, although it wasn't a blatant elbow, he had to go off. In fact he was lucky to be on the pitch after an earlier clash.
By the time Diamonds were down to ten men, they trailed 2-1 anyway but really shouldn't have been losing to a poor Bees side.
Woodman went off after only six minutes and then calamity keeper Jamie Young, who had been dropped after a series of mistakes, gifted the opener. He collected the ball but did not see Dwane Lee lurking behind him to pounce when Young went to roll it out.
Armstrong came on for his debut and within six minutes had a role to play as John Dempster levelled from a corner.
But then ex-Northampton Town right-back Ian Hendon's cross was headed home by Ben Strevens for the winner.