You cannot manage your peers

This argues that you cannot truly "manage" peers because you lack authority; instead you should diagnose why someone is underperforming - skill/clarity gap (can't), disengagement (won't), hidden blockers (blocked), or simple drift caused by a leadership vacuum. The distinction matters because each problem needs a different response: training or clarity for can't, re-engagement for won't, unblocking for blocked, and structural fixes for drift. Drift is particularly common in leaderless small teams, where people slow to the level the environment rewards, so the absence of structure is often the root cause rather than the individuals.

Practical steps are to supply the missing structure informally - propose and document ownership, deadlines and visible commitments - so the team itself applies pressure; make work legible with a shared record of commitments and completions; have direct, impact-focused conversations as an affected colleague rather than as a manager; and protect your own outcomes by decoupling critical paths and keeping neutral records of dependencies and failures. These moves will improve things if drift is the issue. If visible structure doesn’t change behavior, the real constraint is missing authority, and the hard question becomes how long you’re willing to prop up leadership that isn’t yours.