John Anthony's two-for included picking up the key wicket of opener Tom Lance (25) to have United in strife at 36-3 in the 12th over, while Dan Ford would clean out the middle order to finish with 4-33 from his 10.3 overs, including five maidens.
Ritesh Verma, scoring 38 at a run a ball, would try to bat through with the tail, before he was Ford's final victim off a Rayner catch.
Josh Trillo also picked up a pair while Rayner, who got his opposite Gerrard Hobbs and then Robbie Power from the top order, said they took note of the "sweat" from the pitch while it was under the covers.
The bowlers hit their length well and it offered up a lot of edges from the bat which the fielders grasped, he said.
"It was a good toss to win, but Hobbs was just telling me he was going to bat anyway," Rayner said.
Marton then showed how batting on that strip was done, reaching 107-2 in just 20 overs, which will help with the bonus points.
After Scott Oliver departed following a quick-fire start, Hamish Harding (47) took the initiative when joined by Rayner (48no), as they added 63 in 12 overs.
When Harding was caught off a Power delivery, Rayner smacked the final eight runs, with his innings including eight boundaries and a six.
"They gave up on their seamers pretty early," he said.
"They were trying to take wickets. They put spin on but it was manageable."
Both Harding and Rayner had time to wait for the bad balls and then put them away.
This weekend is likely to be Saracens vs St Johns Tech as the only game left to be played amongst the Premier 1 teams, now Marist have departed.
After a disappointing national qualifier knockout tournament and Coastal Challenge Cup campaign, Saracens could end up with the most championships for the Premier 1 teams the summer.
"Maybe the Twenty20 might have turned the screws on the lads and got a bit of confidence in them," said Rayner.
"You noticed it, coming back from the reps."
-Scoreboard
United 104 (R Verma 38, T Lance 25, D Ford 4-33, D Rayner 2-16, J Trillo 2-19, J Anthony 2-34) lost to Marton Saracens 107-2 (D Rayner 48no, H Harding 47, T Lance 1-15) by eight wickets.