This question leads me to a very common issue among sales organizations that I would call a shadow syndrome. This is a prolific problem whereby a great sales person takes over the organization and continues to be a great sales person, overshadowing all of the other salespeople, stifling the egos of the underlings.
Many companies make the mistake of hiring a sales manager to close the big account; those same companies end up with many weak salespeople in need of the 'boss' to come in and close. In that scenario, the sales manager becomes a crutch and can even hinder an otherwise successful strategy. The reason this is a common problem among sales organizations is that the best 'player' usually ends up with the promotion. The reason for the success of that 'player' is deeply tied to the need to win, be aggressive, and a need for recognition. So, in thinking that concept through, the sales leader NEEDS to attract other individuals that have an innate need to win, be aggressive, and a need for recognition. The sales leader, then, needs to fill those needs-recognize them for doing something well, put them in the limelight--to build a truly great sales organization. However, the sales leader typically has those same needs which take a FRONT seat to the needs of the other salespeople, attracting the sales leader to the idea of closing the 'big fish' and taking the limelight. This attraction is like opposite sides of a magnet. I have, literally, seen sales managers in meetings with clients push the sales person aside and take over a presentation, completely missing the opportunity of observing mistakes made and coaching them, along with praising tasks done well.
In answering the question, it's my opinion that in the above scenario, a sales manager will hurt the organization by failing to attract and retain great OTHER salespeople-those prospects will go elsewhere knowing they will only be competing with their prospective boss for recognition. Or, if the great candidates joins the organization, they will be stifled (or shadowed) by the leader and never reach their full potential. A true sales leader will have a massive impact, almost immediately, by attracting great salespeople, training them, ensuring their behavior is consistent with the needs of the company, praising their results, and then getting out of their way.
This leader is a very unique individual: one who has been successful in sales and therefore has credibility; one who has the ability to "shelve" his or her own ego for the benefit of the development of the sales force. The results that follow are tremendous growth and a need for less management.