And McCall knows the young Hearts team have the ability and spirit to bounce back from their defeat by then nearest rivals St Mirren when they turn out at Fir Park on Saturday.
Hearts are 10 points adrift at the foot of the Scottish Premiership but defied the odds with several unlikely results earlier in the season, which they began with a 15-point deduction for going into administration.
So the Well boss will urge his players to put Locke's side under pressure from the off as they bid to record a fourth consecutive home win.
McCall said: "I used to take him to training every day. He never gave me a penny for petrol.
"Billy Brown was there as well and Lockey was on the pro-licence course I was on a couple of years back. He's a really good lad and obviously a Hearts man.
"He will be doing everything in his power, as will Billy, to try to get him out of that bottom spot.
"They have the length of the season and with the backing they have got, you couldn't say that they wouldn't be able to do it because a couple of results can change things.
"It's certainly a hard ask for them and, outwith when they play us, I would like to see them do well because you feel for the supporters and feel for everyone at the club because of what they have been through."
McCall added: "They have to rely on youngsters week in, week out which can be difficult and can be hard on them.
"You are likely to get inconsistency but they are more than capable of putting in a performance like they did against Aberdeen or Hibs and winning the game.
"So we want to make sure we get that first goal and really try to go from there and not give the young lads any sort of hope.
"But it's a tough game on their own merit because they will be desperate and will have a big backing."
Motherwell will make a £1 donation to the Foundation of Hearts, the fans' group in position to take control of the club, for every supporter that pays into the visitors' stand.
McCall said: "Their support has been outstanding and their victories they have had, the Edinburgh derby and Aberdeen, were big games.
"I certainly think they have not got what they deserved when you look at the points tally. A lot of big decisions have gone against them and they have got to feel hard done by."
Meanwhile, striker Henri Anier admits he would like to stay at Fir Park when his loan deal from Viking Stavanger ends in January.
The Estonia striker, who has netted four goals this season, said: "I don't know much about it yet myself. It's between the clubs and we'll see what happens. It's still early.
"I'm really enjoying my time and I really hope I can stay further, until the end of the season at least."