The 33-year-old right-back was substituted with tightness in his left leg after 68 minutes of Northern Ireland’s midweek World Cup qualifying tie against Switzerland.
That raised concerns regarding his availability for the Edinburgh derby but Smith told Neilson he is fit to play despite missing training at Riccarton on Friday.
“I spoke to Michael when he got back,” explained Neilson. “He didn’t train today [Friday], we just rested him. He will train on Saturday and he should be fine. He is an experienced player so you don’t really need to do much with him. He just say: ‘Are you fit to play?’ He said he’s fit so he will play.
“I spoke to him about what happened in the international match. He had been feeling a wee bit tight prior to the game. When he was playing he said it just started to tighten up a wee bit in the second half. He is big enough and old enough now to look after himself in a game.”
Neilson and his coaching staff, Lee McCulloch, Gordon Forrest and Steven Naismith, have stressed the importance of this fixture to Hearts players new and old.
“It comes from the coaching staff first and foremost when you focus on the game and what we are going to work on. The players realise the enormity of it,” said Neilson. “They will have been wandering about the streets of Edinburgh hearing people talk about it, as I have, so the build-up is there.
“When you come into the ground for a derby, you feel the difference between that and a normal home game. You feel the atmosphere building just driving in along Gorgie Road. I always find that, the bigger the player, the better they respond to big games.
“Having fans there is also really important. That’s what the derby is, it’s about the fans. It’s a city derby with both sets of fans at the game generating that rivalry. When you don’t have that it becomes a bit neutral because it’s the stadium that creates the atmosphere. It’s great for the intensity.”