The champions were trailing for long periods to an early Hearts goal and only drew level courtesy of a late Stephen McManus strike. The Bhoys frustrating day was complete with a hamstring injury to midfielder Shaun Maloney
"He just pulled up. It's a hamstring and not very good," boss Gordon Strachan said.
"It was a poor first half by us, one of the worst performances for a long, long time," he said.
"Hearts did well and were physically strong but we were too predictable.
"We built ourselves up to average in the second half and had a lot of possession around their box so it was far more exciting.
"But we had to grind something out so they did well the drag themselves back from such a poor first half performance and give the crowd hope in the second half."
Celtic passed up on a chance to go six points clear of Rangers after the Ibrox club could only draw at Dundee United.
He said: "Maybe Rangers are feeling the same way.
"That will happen until the end of the season, teams will have off days so we must be happy with the point considering the way we played in the first half."