They actually found that out the hard way back on Jan. 9, 2009, when Wafer came off the bench and drilled a quartet of 3-pointers for the Houston Rockets, including one in the final minute to lift his team to an 89-85 triumph.
It was one of just six losses Boston endured at home that season, so it was somewhat memorable, particularly the way Wafer drilled the shot over Paul Pierce and in front of the Boston bench.
Asked Monday if he recalled the shot, Pierce initially played coy, but couldn't keep a straight face.
"Man, I don't remember too many regular-season games," Pierce said before a smile emerged. "No, I do remember. I was guarding him."
Pierce said Wafer hasn't brought up the shot, noting that he's "probably got 20 shots" over Wafer for his career. But Pierce does like what he's seen from the 6-foot-5 guard, believing he has potential to be an X-factor for this team with his shooting off the bench.
"He's learning the system and it's coming along," said Pierce. "He's picking up things nicely and every day he's getting better. He's a really good shooter and scorer. He's taking it all in stride. It's tough coming to a new system. He's learning day by day."
Celtics coach Doc Rivers suggested Wafer hit more shots in that one game than he has so far during the team's scrimmage time early in the preseason. Unfazed, he has stressed to Wafer to keep shooting as he adapts to his new surroundings.
"He's been up and down, but we told him there's a difference -- there's Celtics speed," said Rivers "It's almost the same speech we gave Nate [Robinson]. There's a Celtics speed and there's the speed that Von is playing at. Give him credit, over the last three days he's really started to come on. He's playing harder, he's starting to get our defense.
"I'm not concerned about his offense. I think he is, because he hasn't made a lot of shots yet. But you know he can. I think he's starting to figure me out. I tell him I could care less about the misses, he can shoot. He's a great shooter, so we're not concerned there."
Wafer admits he's somewhat concerned about earning a roster spot. He inked a one-year deal at the veteran minimum that's only partially guaranteed, allowing the Celtics to cut ties cheaply if he's outplayed by a camp invitee like Mario West (though Wafer has already outlived Tony Gaffney, who was considered his chief competition entering the preseason). Wafer said he's simply focused on his own progress right now.
"I'm not really thinking about it, I'm just trying to do the best I can," said Wafer. "I'm in a dogfight. I'm going to fight until the end, just work hard, and if things don't work out here, I'll be ready to go wherever I have to go."
Wafer reportedly has a Plan B with a team in China if things don't work out in Boston, but venturing overseas is not his preference. Particularly not after the way his last basketball journey played out.
After what appeared to be a breakout season with the Rockets during that 2008-09 campaign (he averaged 9.7 points per game in a key bench role), Wafer chased the money while inking a two-year, $10 million contract with Greek squad Olympiakos.
While in Greece, he injured his back, his playing time slumped from almost the start, and he limped back home after playing just three games, hoping to revive his NBA career. His injuries didn't help that cause as his health scared suitors away, and he essentially spent last year out of basketball (inking a 10-day contract with the Dallas Mavericks at one point, but never appearing in a game).
A bit of a journeyman already -- a second-round draft pick of the Lakers in 2005, this is his sixth NBA team in five seasons -- Wafer knows what's at stake in Boston.
"I'm feeling more comfortable each day here,' said Wafer. "I got a chance to play a lot in practice [Monday with Delonte West out with back spasms]. So it felt real good [Monday], I think it was my best day here, getting a lot of run in practice and getting more familiar with what's going on."
After spending nearly all of his time with the third unit at camp in Newport, R.I., Wafer is looking forward to time with the top units when the preseason opens Wednesday night against the Philadelphia 76ers in Manchester, N.H. That's when the dogfight between him and West should really escalate, as two very different players will be trying to show why they deserve to be on this team.
Rivers has already stated the Celtics are looking for scoring at that backup wing position, which puts him in the driver's seat. But West is turning heads based on his scrappy play and workman-like attitude on the practice court.
Wafer said he needs to get his legs under him after so much time away from game action and thinks once that happens, the shots will start falling.
Just like the ones he sprayed against Boston in January of 2009.
"Nobody remembers that shot," Wafer said with a laugh Monday before being told Pierce actually remembers the game-winner. "Oh, for real? Well, it was a good shot. But it was just a regular 3-point shot to me. If another shot like that came up, it's just another shot for me. That's what I get paid to do."
And if he shows he can still be that type of player, the Celtics will gladly pay him to make other teams feel like they did that January night.
Chris Forsberg is the Celtics reporter for ESPNBoston.com. Follow him on Twitter.