They will likely learn a ton from a veteran such as Garnett and develop into an exciting rotation, as well as help out a historically bad offensive rebounding team from 2011-12. Garnett has also stated that he intends to stick around for at least two more seasons.
The only pending departure of the Big Three seems to be Ray Allen, which means the Celtics need some serious help on the perimeter. That was the area that likely cost them a trip to the NBA Finals this summer.
Here are a few issues the Celtics have, and how Mayo provides solutions to those problems.
Other than Rajon Rondo and Avery Bradley, the Celtics had no one viable enough to fill this need.
Thanks to the interior defense provided by anchor Kevin Garnett and the much-improved Brandon Bass, opponents weren't successful in the paint.
Perhaps more importantly, dominant opposing players were often forced into low-percentage outside shots, thanks to the efforts of Rondo and Bradley on the perimeter.
However, Bradley was injured during the Eastern Conference semifinals, and wasn't able to compete in the next round against the Miami Heat.
The lack of athleticism in the Celtics backcourt and from their swingmen off the bench was exposed.
After being the No. 3 overall pick in the 2008 draft with just one year of college at the University of Southern California, Mayo proved himself a viable pro immediately.
In his rookie season with the Memphis Grizzlies, Mayo was named a member of the NBA All-Rookie First Team and seemed headed for perennial All-Star status.
Unfortunately for Mayo, things didn't materialize that way.
Beginning in his third season, Mayo was removed from the starting lineup and began playing primarily off the bench.
At first, he was simply an offensive spark, but he has recently morphed into a much better defender.
With a newly discovered humbleness despite a high stature in the draft, and a dedication to improving at the defensive end of the floor, Mayo has proven he doesn't mind being a strong contributor as a sixth man.
Avery Bradley may retain his spot as the incumbent starting 2-guard, but Mayo would seriously challenge. Even if he doesn't get it, Mayo wouldn't mind whatever role he plays on the C's—as long as they're winning.
If the Celtics expect to contend this upcoming season, they can't rely on the bench output of perimeter players such as Mickael Pietrus, Marquis Daniels and Keyon Dooling (pictured).
Since the Celtics' roster will be night and day from a year ago and it's unlikely they'll re-sign any of last year's end-of-the-year healthy role players, there's nowhere to go but up from the 2012 playoffs.
With that said, backcourt scoring is a major need. Avery Bradley provided some spark in his starting time last year, but he doesn't have the potential to pour in 20 points per game on a consistent basis in the NBA.
Rajon Rondo is a wonderful point guard, but he is definitely pass-first, and although he can score at times, he does not keep opponents honest enough due to his inconsistent jump shot.
Another weapon on the outside for Rondo to work with would be invaluable in dribble-drive situations.
In his rookie year, Mayo averaged 18.5 points per game—proving that he can score in bunches as a pro. In recent years, he simply hasn't had that role with the Grizzlies
Playing alongside Rondo, Mayo could get an inordinate amount of open looks. He is a high-volume shooter, and when he gets into a rhythm, is difficult to stop.
In addition to possessing the potential to be a deadly knockdown shooter, Mayo can craftily get to the basket with his exceptional ball handling skills and quickness.
The quickness that Rondo and Mayo could bring in attacking the basket would force defenses to key in on both of them.
Defenses needing to pay that type of respect would lead to wide open jump shots for the likes of Paul Pierce, who struggles more and more each year to create his own offense due to wear and tear.
Mayo's explosiveness would diversify the Celtics offense, and give the team a source of perimeter scoring that it didn't have the luxury of this past season outside of Ray Allen and Avery Bradley.
The small lineup of Kevin Garnett at center worked for the Celtics...until Avery Bradley's injury.
Then, Ray Allen was forced back into the starting lineup—despite dealing with an ankle injury throughout the playoffs.
He clearly wasn't himself, as he shot poorly for the majority of the postseason, and couldn't keep up on defense due to being a step slow.
Only counting the 2012 NBA draft picks and the return of Bradley, the Celtics have potential for a small lineup that would be wonderful:
1- Rajon Rondo; 2- Bradley; 3- Paul Pierce; 4- Jared Sullinger; 5- Garnett
That lineup–with the substitution of unrestricted free agent Brandon Bass for Sullinger–served the Celtics very well. That is, until Bradley's injury in the East semis against the Philadelphia 76ers.
Bass is interested in re-signing, but will have higher salary demands. Also, six other teams are interested in him, and may pay more and offer a better shot at a title in a long-term commitment.
With Sullinger being inexperienced and Garnett and Pierce not getting any younger, it's unclear whether a similar lineup will hold up in 2012-13 if Bass is gone.
The Celtics should plan accordingly.
The potential new small lineup with Mayo on the roster is downright scary:
1- Rajon Rondo; 2- Avery Bradley; 3- Mayo; 4- Jared Sullinger/Brandon Bass; 5- Kevin Garnett
While Paul Pierce could also be added in here, he is entering his 15th season and will turn 35 in October. Any sort of burden that Mayo could possibly lift off Pierce to preserve The Truth for the playoffs would be vital.
Whether Bass returns or not, the Celtics are loaded in the frontcourt for the foreseeable future, but are severely lacking in the backcourt.
Ironically, according to sbnation.com as I cited earlier, there have been whispers about a Bass-for-Mayo trade.
As long as Garnett doesn't demand an obnoxiously large salary, the Celtics may be able to keep Bass around and go over the top of Mayo's Qualifying Offer to get him.
Regardless, Mayo's versatility would allow the Celtics to play a more athletic lineup, and could even result in Fab Melo spelling Garnett at center at times to preserve the wily veterans for another deep playoff run.
Even if the Celtics have to go the restricted free agency route and offer Mayo more than his $7.4 million qualifying offer, the team isn't built to be a long-term contender at this time.
Kevin Garnett has most likely a maximum of two years left, and Paul Pierce is likely in the same range.
The addition of Mayo will give the Celtics flexibility it currently can't boast with a bench filled with wing players such as Marquis Daniels, Keyon Dooling, and the oft-injured and disappointing Jeff Green. All of them are free agents, anyway.
Unless another viable option emerges with similar athletic and scoring ability, Mayo is the antidote to everything that the Celtics need.
Mayo is young, well-rounded, athletic, and gives the Celtics a dangerous-on-paper small lineup that could spell veterans like Pierce and Garnett valuable minutes during the regular season, and save the Celtics' status as title contenders for at least the next two years.