The signing ban imposed on the Tynecastle club for going into administration, in addition to a 15-point penalty, is biting hard at the Edinburgh club who are 19 points adrift at the bottom of the Scottish Premiership table and odds-on for relegation.
To that end, the club's administrator, Bryan Jackson, confirmed he will make a second bid to have the transfer embargo lifted and will, as one thread of his argument, cite a possible threat to the health and safety of the young players.
"I am really concerned about it," said the Hearts boss.
"I haven't hidden that fact and I have said it from day one.
"You are worried about burnout, you want to give them a rest at the right time.
"It is very difficult. I know a long hard season can take it out of you when you are an experienced player but when you are a young player it is even worse.
"I had it myself when I came into the Hearts first team which was full of international players, at 17.
"I hit the 20-game mark and then the manager took me out of the team because my form dipped and I needed a rest.
"Unfortunately, I can't do that with the majority of them."
Locke has been unable to name seven substitutes in several games recently - there were only five in the 2-0 home defeat to Partick at the weekend - and insists there is "no chance" of filling the bench when Motherwell visit on Saturday.
And when asked if there could come a time when he will be unable to name any substitutes at all, Locke said: "Possibly, possibly.
"At this time of the year unfortunately, there are a lot of bugs going about and two or three of the players have been laid low, Callum Tapping being the new one this week.
"There might come a time when what will happen is that I will have to put a 16-year-old kid who has just left school on the bench, but what can you do?
"It is not getting any better. Danny Wilson was laid low with a tonsillitis bug, he has lost about seven pounds in weight, it has really taken its toll on him.
"Kevin McHattie is struggling with injury, Callum has a bug as well so he is extremely doubtful for the weekend and the other boys who are injured are still out."