Danny Webb revealed Paul McCallum is set to be out for the next four weeks through injury following their 3-0 loss to Grimsby.
A Sam Jones header, a Callum Kennedy own-goal and a Scott Vernon volley sent the three points back to The Mariners even though Orient displayed some fine quality.
Josh Koroma had a couple of chances to add to his hat-trick from last week’s 4-0 win over Newport County but it was not to be for the 18-year-old.
When asked whether McCallum would be back on Tuesday Webb said: “No chance. I don’t think he will be back Tuesday.
“He came back with the injury and I think that we knew even after he was out for a while, he would feel pain in it towards the end of the season.
“And I always said as soon as that pain got too much where he couldn’t move, he can’t go on the pitch.
“So that is the case at the moment, I think we are looking at maybe a month, four weeks, which is disappointing.
“But it is something else I have got to deal with and I will deal with it the best I can.
Webb also mentioned the striker was a huge miss in today’s game where the 24-year-old can win the aerial ball in the box.
He said: “I said that Sandro (Semedo) puts in some great balls into the box and sometimes they don’t look as good balls because no one is getting across the goal.
“And that is something you cannot get on too much at Dalby (Sam) or Josh (Koroma) because they are brand new to it.
“They are 17,18 and they did some other stuff with it. I just said to them afterwards. It is little things like that that you need to learn from Macca (Paul) and that nasty side of it, go and put the goalie on the floor once or twice.
“Even if you give away a foul, let him know you are there and that will come with them. But the fact that we still look like such an attacking threat is great.
“But when you are playing like that you do sort of leave yourself open. We weren’t playing like that for a large part of the season and we still leaving ourselves open at the back.
“Nothing has changed in that department. And when you are down there you have to take a few risks and get yourself out of this hole.
“And if we can sort of get people off their seats in the meantime that would be great.”
One positive the 33-year-old can take away from the game was fans took to social media to praise the youth team’s chemistry as something they have not seen at E10 in three years.
“That is a massive positive. This has been my age group really, who I have moved with through the ranks from the academy," said the O's boss.
“I know them inside out and for me, of course, you want to set a team up to go and win and get something out the game.
“We are in a relegation fight. But at the same time if I can see five to 10-minute glimpses of Alzate (Steven), Koroma, knowing they have been thrown into the lion’s den, and maybe next year hopefully League Two, maybe conference we will have a hell of a team.
“Sometimes teams have to take that step back for maybe two forward. And that is not a case of us giving up, it is just a case of saying for the first time in a long time, people can look at players on their own, and say alright today is a bit bleak, in terms of where we are. But tomorrow could be very bright.”