Michael Pittman is a man of his word -- the Colts wideout did NOT give up his #11 jersey number ... forcing Carson Wentz to now take the #2 in Indianapolis.
A Colts official tells TMZ Sports the team's newest quarterback will officially change numbers this season ... after he rocked the one-one for his entire 5-year Eagles career.
Unclear why the choice of #2 -- but perhaps it has something to do with him being the No. 2 overall pick in the 2016 NFL Draft .