EXHIBIT 5.1

[Sonnenschein Nath & Rosenthal Letterhead]

October 6, 2006

The Management Network Group, Inc.
7300 College Blvd., Suite 302
Overland Park, KS 66210

Re:  Registration  Statement on Form S-8 in connection with the  registration of
     300,000 shares (the "Shares") of common stock, $0.01 par value (the "Common
     Stock") of The Management  Network Group, Inc. (the "Company") to be issued
     under the 1999 Employee Stock Purchase Plan (the "Plan").

Ladies and Gentlemen:

In  connection  with  the  preparation  of  the  above-referenced   Registration
Statement (the "Registration  Statement"),  which is being filed on or about the
date of this letter on behalf of the  Company,  you have asked us to provide you
this opinion letter  pursuant to the  requirements of Form S-8 and in accordance
with Item 601 of  Regulation  S-K  promulgated  by the  Securities  and Exchange
Commission.

In  connection  with this  opinion,  we have  examined and relied upon,  without
further  investigation,  the following in connection with rendering the opinions
expressed  herein:  (a) the Plan and related  prospectus;  (b) the  Registration
Statement;  and (c)  such  other  documents,  certificates,  records,  and  oral
statements  of public  officials  and the  officers  of the Company as we deemed
necessary for the purpose of rendering the opinions expressed herein.

In our  examinations,  we have assumed the  genuineness of all  signatures,  the
legal  capacity  of  all  natural  persons,   the  authenticity,   accuracy  and
completeness  of all documents  submitted to us as originals,  the conformity to
original documents of all documents submitted to us as certified,  conformed, or
photostatic  copies or by facsimile or electronic  mail, and the authenticity of
the originals from which such copies,  facsimiles,  or electronic  transmissions
were made.  In our  examination  of  documents  executed  by  persons,  legal or
natural,  other than the  Company,  we have  assumed  that such  persons had the
power,  corporate  or  otherwise,  to enter  into and  perform  all  obligations
thereunder  and that such  documents  are valid and binding.  In rendering  this
opinion,  we have assumed without  investigation  that the certificates or other
records  evidencing  the  Shares to be issued  under the Plan and the  ownership
thereof  will be in  proper  form and will be duly and  properly  completed  and
properly executed.

Based upon and subject to our examination  described herein and the assumptions,
exceptions,  qualifications,  and  limitations  set forth herein,  we are of the
opinion that the Shares to be issued  under the Plan will,  when issued and sold
pursuant to and in  accordance  with the Plan and upon receipt by the Company of
the consideration  therefor,  be validly issued, fully paid, and non-assessable.
The foregoing  opinion is limited to Shares that are originally issued under the
Plan.

This opinion  letter is limited to the  specific  legal issues that it expressly
addresses,  and no  opinion  may be  inferred  or  implied  beyond  the  matters
expressly  set  forth  herein.  We  express  no  opinion  as to  the  law of any
jurisdiction other than the General Corporation Law of the State of Delaware, as
amended. We are not admitted to the Delaware Bar. In expressing our opinions set
forth herein, we have reviewed and relied upon,  without further  investigation,
such laws as published in generally available sources.

We consent to the filing of this opinion letter, or a reproduction  thereof,  as
an exhibit to the Registration  Statement.  In giving such consent,  however, we
are not  admitting  that we are within the category of persons  whose consent is
required under Section 7 of the Securities Act of 1933, as amended, or the rules
or regulations promulgated by the Securities and Exchange Commission thereunder.

This  opinion  letter is  rendered on the date set forth  above,  and we have no
continuing  obligation  hereunder to inform you of changes in the applicable law
or the facts  after such date or facts of which we become  aware  after the date
hereof,  even though such changes or facts could  affect our opinions  expressed
herein.

                                Very truly yours,

                                /S/ SONNENSCHEIN NATH & ROSENTHAL LLP

                                SONNENSCHEIN NATH & ROSENTHAL LLP