Rivals by Leo Rivers

He signed up to be hunted—but he never expected his rival to be the one catching him.
Buttoned-down human Nick has spent years butting heads with wolf shifter Viktor—his arrogant, insufferably handsome coworker. When they clash in meetings, Viktor always finds a way to come out on top.

Nick hates him. Truly.
Which is why he never expected to run straight into Viktor on the mating run.
One night. One chase. A pack of anonymous werewolves free to take what they want from a human. It was supposed to be simple—one secret night of pure submission.
But now, the man who’s spent years challenging him in the office has him pinned down in the woods.
And this time? Viktor definitely has the upper hand.
But if Viktor thinks Nick is going to roll over without a fight—he’s dead wrong.

Rivals is a high-heat knotty wolf shifter/human enemies to lovers romance with a HEA. It’s part of the Mating Run series, but can be read as a spicy little standalone.