I'm about to pick up line management of someone who himself has a team of 6 staff. I've managed staff for years, but never anyone who has responibiliuty for others' performance.
My new direct, Jack, isn't performing well. There are sickness absence issues, missed deadlines, poor quality work. I don't yet know how well he manages his staff but I think I see poor performance & a sloppy attitude in the staff team too. They might think they're doing ok? I don't yet know if they've had feedback or our version of regular O3s.
My question is which order do I tackle things in? My gut feeling is in 3 months Jack will have resigned or been sacked. My colleague has tried to handle his performance over the past year and not made any noticable change. Should I start managing his staff directly myself so they have the best possible chance to improve? OR should I try to manage them through Jack? How?
I look forward to any thoughts you might have. Thank you in advance.

Help?
Pick up starts on MOnday and I don't have a plan. If you are aware of resources I could use or have experiences I'd love to hear.
The first 90 days
Don't assume anything. Start with one on ones, and pay attention to what's happening (behavior, not characterizations)
Gather your data, independently of the past. Give him a chance to show you what he does, and how well his team performs.
Let Jack handle the team for now. If this has been going on for a year or more, a few more weeks aren't a big deal. You won't know what's best until you observe, for yourself, what's happening.
John Hack