Doc Rivers knew it could happen if Rajon Rondo let it.

“Bottom line is, when you shoot, you’re the shooter,” Rivers said following the Celtics-Bucks game on Tuesday. “And that’s what I tell him all the time. Once you decide you’re shooting, there is no one else open but the rim. And that’s it.”

On Thursday night against the Wizards, Rondo decided he was shooting ... 20 times to be exact. And his decision to go on the offensive played a key component in the Celtics' 104-102 victory over the Wizards in Washington. (Recap.)

His 20 attempts tied a career high, previously set last March 18 against the Heat. Here are three lessons from a night when Rondo wasn’t the only guard with a career milestone:

FOR RONDO, 'ONCE IT'S YOUR SHOT, IT'S YOUR SHOT'

Rondo got out to an early start filling up his stat line.

He posted four points, two assists, and two rebounds in the first 7-1/2 minutes before heading to the bench with a pair of personal fouls. He didn't check back in until 6:05 left in the half. That was more than enough time to get the job done.

Rondo scored 21 points on 10-for-20 shooting in just under 38 minutes. His 20 attempts tied the Celtics’ previous season high set by Kevin Garnett on Nov. 6 against the Suns. (The difference is, the Celtics lost to the Suns and won this game.)

“Clearly [the Wizards'] game plan was they weren't going to guard him,” Rivers told reporters after the game. “They were going to give him shots, and he took them.”

There were drives to the basket, with a couple of his awe-inspiring lay-ins here and there. And there is no doubt that his baseline dunk with a minute left will make the highlight reels. But the most impressive aspect of his performance was his willingness to pull up for the jumper. The shot that had been deemed his weak point looked effortless at points.

“That's what we tell him — once it's your shot, it's your shot,” Rivers said. “There's no more passing or being a point guard. When it's time to shoot, it's time to shoot. You're a shooter. And I thought he did that tonight.”

Rondo added 11 assists to his 21 points. For this night, at least, being a shooter and a point guard were not mutually exclusive.

SO THEY CAN GET ON THE GLASS

In spite of the Celtics’ nine-game winning streak entering the game, the Wizards held a clear advantage. They can rebound. As for the Celtics, well, that hasn't always been so easy to tell.

The C's were ranked 29th in the league in rebounding (37.9 rpg); the Wizards were ranked third (43.6 rpg). Take a look at each team's leading rebounders prior to the game:

Wizards: Brandon Haywood (10.8), Antawn Jamison (8.7), Caron Butler (6.9)

Celtics: Kendrick Perkins (7.5), Kevin Garnett (7.4), Paul Pierce (4.6)

After being outrebounded 44-35 by the Bucks earlier this week, the Celtics could not afford to slack off with an obvious disadvantage.

“It becomes a physicality [issue],” Rivers said Wednesday on WEEI's Dennis & Callahan show. “You start relying on just going to get the ball instead of making contact. You get into those habits. That’s what happened. It’s amazing. We’ve worked on it. We’ve talked about it and we’ve proven we can do it in stretches. We did it [Tuesday night against the Bucks] in the last five or six minutes of the game. I’ve mentioned words like team improvement, the little things. That’s part of what we talk about and those are the little things that we do have to improve on, and it’s a problem right now.”

The need to improve was noted. Even though the Celtics did not rebound consistently for 48 minutes, they put together a second quarter in which the Wizards did not grab a single board. The C's had a 20-8 advantage at halftime and won the battle of the glass, 40-34.

Haywood was held to eight rebounds, more than two below is season average. Perkins, meanwhile, posted 11.

“It says that we can rebound, which we were questioning before the game,” Rivers said after the win. “It's just amazing when you focus on something how well you do it. But that's something that we have to improve on. This is a hell of a rebounding team, Washington, and so we had a big focus going into this game about keeping them off the glass.”

The Celtics will have to work just as hard on the remainder of their road trip. The Bulls and Grizzles are both averaging more than 42 rebounds per game.

ALLEN ENJOYS A 'WONDROUS ACCOMPLISHMENT'

Ray Allen needed 14 points to achieve his “wondrous accomplishment.” It took him just three quarters to attain it.

Allen scored his 20,000th career point on Thursday night. He currently ranks 33rd in all-time career points and is just 45 points from surpassing Tom Chambers for the 32nd spot.

“Twenty thousand to me is a wondrous accomplishment," Allen said on Tuesday. "I think for the most part it's all about longevity and staying healthy, taking care of my body, being on some good teams. But you think about all the great assists that lead to a lot of those baskets, so it does allow me to reflect on the guys that I played with, the coaches that allowed me to make the game easier, just understanding the game.”

Allen finished the game with 18 points, bringing his total up to 20,004. He is ranked fifth among all active players, but don't expect him to move up in that group too quickly. Kevin Garnett is ranked fourth.