Defoe has struck 14 goals this season to give his side a glimmer of hope in their latest survival mission, and his impact has never been more required than Saturday's potentially crucial Premier League clash with travel-sick Burnley.
With his club reeling from the news defender Jan Kirchhoff's recovery from a knee injury will be delayed by at least four weeks, Moyes believes Defoe's international revival could have been particularly timely.
Moyes said: "I think it's a boost to Jermain and hopefully it gives the whole club a lift because we need his goals and we need more goals.
"It's less and less likely that older players get call-ups when they've been out of the team for a while
You get players like Steven Gerrard and Wayne Rooney who play right through to their mid-thirties, but when you've been out of the squad, it shows your professionalism in never giving up on it."
Moyes had hoped to bring the influential Kirchhoff back into contention after three months out with hamstring and knee injuries, but the German suffered an adverse reaction after playing an hour of a recent under-23 match against Manchester United.
He added: "Jan has unfortunately had a recurrence of his knee problem and it looks like it is going to keep him out for a minimum of four weeks.
"I don't think there is any damage, but it is going to take longer than we thought to heal."
Sunderland go into Saturday's game six points adrift of safety and, on the face of it, could hardly have wished for more favourable opponents than the Clarets, who have taken just two points on their travels so far this season.
But after a string of solid performances from Sean Dyche's men in recent games - not least last week's excellent display in a narrow 2-1 defeat at Liverpool - Moyes is wisely guarding against any complacency.
And he believes the fact many members of his side, not to mention the Black Cats supporters, have been through similar relegation battles all too recently could give them a vital edge in the increasingly pressurised run-in.
Moyes said: "They (Burnley) have been tough opponents for a lot of teams
Their away form has been mentioned but they have had a really solid season - they're a tough team to play against and they make it difficult for you.
"I think sometimes you've got to say yes, it's a really important game, but for us there's other games to come as well.
"The supporters have always been important but they've been in this position before so they're used to it, and many of the players are used to it as well
They've used their experience in the past, so let's hope they can do it again."
Source : PA
Source: PA