The Australian signed a new five-year contract with the Scottish Premier League champions after returning from a three-week spell on the other side of the globe playing in his country's World Cup qualifiers.
And he may further demonstrate his commitment to the Parkhead club by foregoing an extra break given to players involved in international duty.
McDonald, who scored 31 goals for Celtic following his £700,000 move from Motherwell last summer, said: "Coming back to the ground after three weeks away, I'm chewing at the bit again, albeit I need a bit of a rest.
"I've just finished with international duty, so I will get a couple of weeks away and refresh the body and the mind and come back as hungry as ever.
"I think everyone is back on July 4 but everyone who has been on international duty is allowed an extra break.
"I'm weighing it up at the moment and will see how I feel after the next couple of weeks, and see how refreshed I feel.
"If I feel good enough, I'll be back the same time as everyone else, because I don't really like missing out on anything.
"I like to know I've done the same as everyone else. It's what's best for me, and best for me would be to come back at the start of pre-season.
"I believe if you have a very good pre-season, it could make the difference for the rest of the season."