City made the most of their game in hand by putting four goals past Cork City at the Brandywell to propel themselves into third place in the table.
Eoin Toal and Junior both scored just before half-time to give Derry a comfortable lead at the break.
An unfortunate own goal from Horgan, after a header from Junior was saved made it three for the Candystripes before Junior scored again just before the final whistle.
City’s next game is away to Dundalk on Friday 4th October.
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