"Aberdeen had a brilliant start and opened up a a significant gap but, slowly but surely the teams below have been chipping away.
"We've got the opportunity to close it further in a few days. If we can get a similar level of performance to what we showed here, we're capable of winning that one."
St Johnstone knew victory would lift them off bottom spot but they are now two points adrift of Hearts having played half of their league fixtures.
Kirk's angled shot after a neat turn capped a bright first half for the hosts, but they could not build on it in the second half as Goodwin's half-time message paid off.
Middleton cut in from the left and fired a right-footed effort low in off a post past Josh Rae, who appeared slightly slow to get down to try to make the stop.
Then Vicko Sevelj put in an excellent delivery for Dalby, who did not pass up the gift as he rose to power home and bolster his place at the top of the scoring charts with nine this season.
After Gallagher's sending off, Jack Sanders was closest to an equaliser for St Johnstone but his powerful header was tipped over as the home side suffered a third-straight defeat by a single goal.