The Queens Park Rangers under-23 keeper will continue to deputise for the injured Jack Harding after being signed on a month-long loan.
Ford said it makes sense to continue with Herdman, who impressed on his debut against Kings Langley. That will give Harding more time to recover from a knee injury that he aggravated in training.
“Jack tried to train on Thursday but his injury was worse on Friday, so it makes no sense to bring him back in too soon,” he said.
“The way Martin played on his debut means I can rely on him, he’s a very mature keeper. Queens Park Rangers were very good about loaning him to us.”
But Charlie Hawtin has been ruled out for the rest of the campaign after breaking a bone in his ankle late on against Kings Langley.
Ford said: “Charlie has been fabulous for us and it’s disappointing for him. But I’m glad we put him on a contract because if I was a manager at the next level, he’d be on my radar.”
Jack Self should have recovered from the illness that ruled him out last Saturday as Ford looks to extend United’s excellent away form. United have only won five games at home compared with ten on the road.
Ford added: “I want us to keep trying to win games and so do the players. But I’m also looking to try a few things in the remainder of the season.
“I’m reasonably happy with the squad, in certain areas we’re getting things into place for next season.”