The Dunscroft fighter will face Yafai for the WBC International super bantamweight title in Sheffield on March 3 in a genuine 50-50 contest.
McDonnell is aiming to secure another world title shot after falling short against Rey Vargas last February while Yafai is hoping to edge closer to his first attempt at world honours.
“It’s a brilliant fight that both guys will fancy,” Coldwell said.
“Gavin wants to get back to world title class immediately, and Gamal wants to get there for the first time.
“Gamal is someone I consider a good friend, and I can’t say enough about how highly I rate him, but boxing can sometimes create these situations.
“It’s a massive reward fight for both of them because the winner will be in line for something big, but our efforts and concentration have to be on nothing but Gamal for the time being.
“He’s came through very impressively so far in his career, and the brilliant amateur success he had looks like being transferred over.
“Despite all his talent, he’s missing experience, and that is the one big advantage that Gavin can make count for him.”
McDonnell and Yafai have been regular sparring partners in the past but Coldwell does not believe that will have any bearing on their March contest.