The Northern Irishman, who has scored ten goals in 15 appearances this season, was replaced on the hour-mark by Armand Gnanduillet and Neilson revealed the 30-year-old will need to be assessed.
“We will see how he is on Sunday,” said Hearts boss Neilson. “He had a tightness in his calf and he is such a key player that we took him straight off to try to make sure he is all right. We will see how he is for Wednesday.”
The Jambos let two points slip from their grasp after Jason Cummings cancelled out John Souttar’s opener at Tynecastle.
"If you look at the bigger picture, we are sitting top of the league after ten games,” said Neilson. “Yes, we are disappointed not to have taken maximum points after the way we played and the amount of chances we created, but I can’t fault the players for their effort and the way they tried to win.
“But when you are 1-0 up and you don’t get the next goal, you are always susceptible to losing one.
“You are always going to have games where you don’t have that final moment, but the key phrase is that we are getting the moments. We are getting into really good areas, having shots. Some days, it just doesn’t go in.
"We limited them to very, very few chances. They got a throw-in, we didn’t make first contact on it and, when you do that, you leave yourself open to losing a goal.
“The key thing is that we didn’t get the second goal.
"When we don’t win, there is a disappointment from the dressing room whether it is Rangers, Celtic, Dundee or Ross County.
“We expect to go and win the game. We didn’t win it today , but we had the chances to win it and the performance to merit it, but we have to accept the point and move on. We are undefeated after 10 games on our return to the top flight and the mood inthe camp is very good.”