Sales managers should manage, not sell
A true sales manager should never sell. This is a potentially fatal mistake that can utterly demoralize your sales team. Having your boss compete for leads creates a less than desirable sales culture and raises questions of objectivity. On top of that, sales managers are often too busy working their own leads to bother coaching and mentoring the salespeople working under them.
Source: Sales consultant Bob Croston
Great managers know that their primary responsibility is to place those they manage in the best possible position to succeed. Selling against the team destroys any respect the staff has for the manager and creates a toxic, underperforming sales environment.
If you need your sales manager selling, it's possible that you are not ready to have a dedicated sales manager. In this case, the CEO, Vice President, or General Manager should take on the sales management role.
The responsibility of a sales manager is to attend to these five things and these five things only:
1. Holding sales people accountable
2. Developing the team with training opportunities
3. Coaching sales professionals
4. Motivating sales staff
5. Recruiting new talent
Regardless of what you call him or her, someone needs to take responsibility for these things, and it should not be someone who is also responsible for selling.