Hartson, who won the league title in Scotland with Celtic three times, may not be popular among the Rangers fans, but the Ibrox faithful will agree with the 43-year-old former Wales global striker's comments.
All hope that this afternoon's Scottish Cup semi-final between Celtic and Rangers would offer a competitive, enticing spectacle definitely fell away shortly after the second-half began.
"The history is enormous at this club and what we did a year ago was historic", said the Parkhead boss.
"The important thing now is to close up the league".
However, the former Hoops manager and player doesn't reckon Brendan Rodgers will start with both for the Hampden showdown. "They work hard and won't make it easy".
"That isn't to say that the two of them might not end up on the pitch at the same time. We have a way of playing that we know can win games".
Tomorrow at Hampden, Celtic have a chance to extend that...
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Tom Rogic, Callum McGregor, Moussa Dembele and Olivier Ntcham scored Celtic's goals against Rangers, which had Ross McCrorie sent off early in the second half.
The Celtic boss told BBC Radio Scotland: "I was very proud of the team".
"They looked like they were trying to block the middle but that gave us space down the side", he continued.
"We had fairly decent control without too much threat against us".
"We have had a really good training week and we enter into it to win".
"I never become complacent", he said.
"However, for me, Dembele just edges it going into these games".