The 5yr-old produced a big finish along the passing lane to upset punters and score a bonus win for his connections.
Breen said after his pacer's victory at $25 odds on Monday he had no intentions of starting the horse in the race.
But when the Northern Southland Trotting Club $13,799 Summer Cup was running light on nominations, he threw Sagwitch's name in the ring.
"I wasn't going to start him but they were ringing up looking for horses.
"He was meant to race at Winton next because it's penalty-free, but that won't matter because this stake was twice as much."
The win was no surprise to Breen.
"How he went - that is what he feels like when you work him.
"He just hasn't had any rub of the green. The start of his last start at Roxburgh was shocking and then at Winton before that he got savaged and then carted back. But he ran on at the finish and the start before that he ran fourth."
Breen has amassed 11 wins since Loretta Franco scored at Winton in September,
eclipsing his previous best season tally of
seven winners in 2017-18. He praised his drivers, who include Mark Hurrell, Brad Williamson and Allan Beck.
"The boys have been driving them all good.
"Santanna's Rocket was always going to do a good job once we got him sorted out. I was a little bit disappointed with him today, but perhaps he just pulled a bit hard in behind them. He is a free-going horse."
Santanna's Rocket finished seventh behind Sagwitch.
The third of Breen's runners, Mucho Macho Man, ran eighth.
It is a case of Ascot Park one day, Gloucester Park the next for breeder-owners Syd and Shona Brown.
The Mosgiel couple warmed up for what could be a big weekend when their pacer, Diego, scored a deserved victory yesterday.
Their blue and gold colours will be aboard their star pacer, Field Marshal, who will start as the hot favourite in tonight's group 1 Fremantle Pacing Cup.
Diego broke maiden ranks and a frustrating run for trainer-driver Jonny Cox when winning by a half-head.
All his team had finished in the first six over the festive period but he had been unable to crack a win until yesterday.
"He is a nice horse and I have always had a bit of an opinion of him," Cox said of Diego.
"He has just had a run of little things that have niggled him on the way."
Cox drove Diego to make use of his high speed, holding him up until he was balanced in the home straight. He unleashed a big run to nab Prince Abbey just before the post.
The Browns should not have to wait until the home straight to see Field Marshal unwind. The 7yr-old is drawn to lead and dominate his 2536m feature from barrier 2.
