Grant's side are heading for the FA Cup final and the second tier of English football off the back of debts totalling a staggering £119 million.
Through it all, however, the former Chelsea boss has conducted himself superbly, according to Coyle.
The two men go head-to-head at the Reebok Stadium on Saturday and Coyle said: "We have tough enough jobs as managers without getting caught up in financial controversies.
"Anyone who can take a team to a cup final like Avram is doing something right. He is doing a terrific job.
"What he has done, because he is such a quality manager, is galvanise the players. They have a spirit in adversity. He has used that and been clever with it.
"Regardless of who plays for them, there is a determination to win games and be a credit to Portsmouth. All credit to Avram, he is a top class manager but we knew that anyway."
Coyle is hoping Matt Taylor can continue his good form after shaking off a bout of glandular fever.
Taylor showed he was on the mend by scoring a brace in the victory against Stoke on Saturday, which all but secured the club's top flight status.
It was little wonder he celebrated after complaining of feeling unwell following the Blackburn match in February.
Coyle said: "Matt felt ill and we had him tested after the match. It showed he had glandular fever at some point although they can't pinpoint exactly when.
"We all recognise the qualities of Matt Taylor. He showed that last week and I am delighted for him.
"He works ever so hard every day in training. I always feel when players work as hard as that they get their rewards."
Taylor is now set to face his former club Portsmouth and Coyle added: "It is a special game for everyone, not just Matt, as we want to secure our status.
"Matt is in terrific form and we want him to continue like that. He has tremendous feeling for Portsmouth but his loyalty is to Bolton and he will be doing his utmost to try and win the game."
Source: Team Talk
Source: Team Talk