Matt Calcott's visitors lifted their effort in the second half, but were unable to find a goal with Waitakere still enjoying the better the chances.
Jake Butler arrowed an effort inches wide soon after the restart while Futsal White Dylan Manickum saw scoring opportunities go wide of O'Keeffe's post mid-way through the half while the Team Wellington goalkeeper tipped over goal-bound David Mulligan free kick 25 minutes from time.
At the other end, Luis Corrales headed an Ian Hogg cross goalwards only to have it blocked by Shelley before Richards completed the scoring in the 75th minute, his second of the game coming in the aftermath of a goal mouth scramble.
Shelley was understandably delighted with his side's effort as they confirmed their playoff place on their terms with confidence high in the group.
"I thought it was an outstanding performance by everybody," Shelley said.
"We seem to really raise ourselves for these bigger games and any of the so-called top teams. We've competed with them all season.
"Today was pretty one-sided; we dominated the game from start to finish. We put out an attacking line-up with some creative players going forward. I thought our front three were excellent but you can't just single them out.
"Danny Robinson gets off a plane at 7 o'clock this morning from Spain and he wants to play and that's the sort of group we have.
"The goal was to get in the top four and I think we can compete with anybody now once we're in there."
Calcott said a weak opening period - one of his side's worst of the season - proved costly.
"We didn't come out of blocks did we really," Calcott said
"It was probably the most disappointing first 30 minutes we've had in the last six months. It probably doesn't help that there was nothing on the game for us.
"They stepped up and for a number reasons we found ourselves 3-0 down but [we're] happy with the second half performance."
Turning to the playoffs starting next week - with their opposition to be confirmed on Sunday, Calcott said the first priority is getting some players missing from Saturday's clash back involved.
"We had some people on the bench today sitting on suspensions and we had three injuries. From our side it's getting four or five back and that will make a big difference to this squad."
Saturday's result sees Waitakere United move into third place while the Wellington Phoenix loss to Auckland City confirmed Hawke's Bay's playoff spot ahead of their decisive clash with Canterbury United at Bluewater Stadium on Sunday.
A win for Hawke's Bay United would see Brett Angell's side leap-frog Waitakere United into third place and earn a playoff meeting with Team Wellington.
Auckland City trounce Phoenix
ASB Premiership minor premiers Auckland City FC warmed-up for the semi-finals with an emphatic 7-0 win over the Wellington Phoenix at Newtown Park on Saturday.
With the hosts needing a win to keep their own playoff hopes alive, the visitors made no race of it, claiming their 10th straight victory since dropping their first game of 2015 against the same opponent back on January 11.
Ramon Tribulietx's side opened the scoring in the 20th minute as new All Whites striker Ryan De Vries slotted home a cross field pass from Joao Moreira.
The visitors were 2-0 up just four minutes later, Oscar Garcia heading home De Vries' cross on the end of a counter attack and just after the half hour it was 3-0 as Moreira struck from the penalty spot after Louis Evans had felled Garcia in the area.
It got worse for the hosts before the break, Auckland City going 4-0 up as Moreira grabbed his second; finishing off an excellent cross from fullback Takuya Iwata two minutes before the whistle.
The halftime margin could have been even greater but for an excellent double save from goalkeeper Oliver Sail which denied Garcia and Ivan Carril earlier in the half.
Entering the game as the league's top scoring side, the Phoenix had few sights of Tamati Williams' goal in the first 45 minutes - Andrew Blake's 20-yarder which cleared the crossbar the best of it.
Although the hosts threatened to get on the scoreboard early in the second spell, Ruairi Cahill-Fleury shooting against the crossbar, Auckland City were 5-0 ahead 10 minutes after re-start - Carril tapping in after Sail had parried an initial shot, the strike pulling the visitors level with the Phoenix on 37 goals for the season.
De Vries' second of the day made it 6-0 on the hour as Auckland City became the league's top-scoring outfit across the regular season and Andrew Milne scored what turned out to be the final goal when he made it 7-0 in striking home a loose ball at the back post with 17 to go.
Tribulietx said after the match he was happy with the effort of his charges against what was an inexperienced Phoenix line-up.
"We were playing against a very young team, we have to acknowledge that," Tribulietx said.
"I think we played a good game, we had a lot of the ball. Especially after 10 or 15 minutes once we settled down we dominated and quite a lot of chances.
"For us it was just a matter of making sure we competed well because that's the best way of preparing for the semi-finals and we did that so we have to be happy with that."
Saturday's result is the 10th successive win for the league leaders but Tribulietx says the focus remains on the process rather than the outcome as the playoffs begin next week.
"We want to make sure we keep this dynamic of good football, we compete well in and out of possession. We've regained our intensity in the attacking half, which is important for us."
"We're reaching the semi-finals in a good moment but we know it's going to be a different story. The team we're going to play against, whoever they are, are going to start at the same level as us so it's like a different competition."
Wellington Phoenix coach Andy Hedge acknowledged the gap between the two sides on the day.
"We said at halftime to the staff that it was probably one of the best 45 minutes of football I've seen from any team this year," Hedge said.
"Auckland really deserved the not only the result today, but the league as well, and we were miles off our game. If we look back to the game against Auckland when we won up there, we had a really good game and they had an off day. To compete against these sorts of teams you can't have an off day.
"They were outstanding; their movement, the fluidity of their midfield, the speed of the ball and their quality of finishing and to be honest it probably should have been more."
Having reached the end of their debut season in the competition, Hedge says the club are happy with returns on their involvement.
"I think it has ticked every box for the club," Hedge said.
"It's allowed the professionals to play to keep them ticking over and it's given us an insight into which players coming through the academy can stand up to the next level.
"All in all it's been a really successful venture for us."
