After falling behind 2-0 to the Miami Heat to start the Eastern Conference Finals, experts said that the Boston Celtics were too old, too slow and incapable of competing for another championship. Now, they stand just one win away from a return trip to the NBA Finals– for the third time in five years.

The pulse still beats strong within these aging Celtics, as evident in their shocking 94-90 Game 5 victory over the Heat at American Airlines Arena on Thursday. They maybe old, but the C’s can still compete. And now, Boston’s Big Three find themselves with a decisive 3-2 advantage over the much younger and athletic Big Three of Miami, who were assembled to dethrone them in the East.

Although, the Celtics’ –who some would say have overachieved this season– star power has faded over five years since the Big Three were first acquired, the seasoned veterans have relied on their championship core to push forward in these playoffs, and no one has been more important than the eldest statesman, Kevin Garnett. Alongside the incomparable Rajon Rondo, Garnett has channeled his former league MVP self and elevated his game to its highest level. Rondo’s been brilliant, but KG’s production this postseason has been unreal.

According to ESPN Stats & Information, in this year’s playoffs, the 36-year-old ranks first in double-doubles in the playoffs, first in rebounds, third in minutes, fifth in points, fourth in blocks shots, eighth in steals– and he’s tied with the newly crowned NBA MVP, LeBron James, for the most points in the league in the fourth quarter, with 104. If Rondo is the Celtics’ powerful engine, then Kevin Garnett is the fuel that makes the motor run.

After the Celtics stole Game 5, ESPN’s Doris Burke asked what fuels KG’s motivation. The always outspoken, future first-ballot Hall-of-Famer, simply stated the haters. “Competition. The naysayers. The owners who talk too much. The people who don’t think a 35 or 36-year-old can do what I do,” explained KG. “I take a lot of pride in my craft. I work really hard on my craft everyday. I’m a true professional.”

Garnett’s been a true professional indeed. His 7-foot-6 wingspan has been the antidote against the penetration of LeBron James and Dwyane Wade. According to AccuScore, Boston is an astounding plus 164 this postseason with Garnett on the floor and a alarming minus -119 when he sits. The percentage has gotten stronger against the Heat. Miami has blown out the Celtics by 25 points in the 49 minutes when KG’s been on the bench. And they’ve been down by 19 points in the 153 minutes that he’s been on the court. On Thursday, Garnett, formerly known as the Big Ticket, finished with 26 points and 11 rebounds, including sinking a crucial pair of free throws in the waning seconds to put the Celtics ahead by four points for good.

KG’s production on both ends of the court will become more invaluable if Chris Bosh starts Game 6 for Miami. Bosh convincingly outplayed Garnett in the Eastern Conference semifinals last season, but with the Heat’s All-Star recently returning from an abdominal strain –that sidelined him for nine games– the Celtic’s power forward will look to capitalize on the less-than-healthy Bosh at every point.

In Boston’s Big Three era the Celtics are 9-0 in Game 5′s when the series is tied at two games apiece. The team many experts said were too old, too fragile, too handicap to win this series; are now up 3-2 in the conference finals, with a chance to turn off the Heat permanently on their parquet floor in Game 6 on Thursday. “Nothing’s easy, we do it together. We don’t do it individually,” KG told Burke. “And when we do that, we look bad. But when we do it together, we look pretty darn good.” Age ain’t nothing but a number and the Celtics’ Big Three are ready to prove all doubters wrong on Thursday.