Jim Mallinder was ‘very frustrated’ after Saints suffered a second-half shock at Sandy Park.
The men from Franklin’s Gardens had gone in 12-3 up at half-time thanks to tries from Lee Dickson and Ken Pisi.
But their dominance was turned on its head as Exeter fought back, scoring 17 unanswered points after the interval to secure a 20-12 win.
It was a disappointing outcome for Saints, who had put themselves firmly in command, but who eventually failed to even earn a losing bonus point.
And Mallinder said: “I’m very frustrated.
“It was a very good first half, playing with the wind and we played well, took our opportunities at the right time.
“We counter-attacked well and defended when we were under pressure, but second half we didn’t play particularly well.
“We coughed up a lot of ball and our set-piece didn’t function as well as it had done.
“We probably kicked away a bit too much and we were put under pressure defensively.
“We went down to 14 men and we gave away too many points.”
Saints fell foul of referee Greg Garner’s whistle on a number of occasions during the second period, giving away 10 penalties.
Mike Haywood’s 48th-minute sin-binning proved key as Olly Woodburn scored while the hooker was off the field.
And Mallinder said: “It’s crucial. If you go down to 14 men against the wind away from home, it’s going to be tough - and so it proved.
“We just didn’t get the rub of the green.
“Exeter were good in the second half and put us under a lot of pressure, but again we just didn’t get that bounce of the ball.
“There were a few refereeing decisions that went against us.”
Saints were denied a last-gasp George Pisi score that would have earned the bonus point, with Garner harshly ruling against Jamie Gibson in the air.
“I thought it was a poor decision from the referee,” Mallinder said. “He made the ruling.
“Jamie Gibson went up for the ball in the air and competed for it honestly.”