The 7-day DL was created in 2011 as part of the league's concussion protocol.
In a corresponding move, the Rockies recalled Rafael Ynoa from Triple A.
Morneau, who turned 34 on Friday, appeared to injure his neck during Wednesday's game on a dive. Morneau has suffered a number of concussions over the last few seasons, missing substantial time in 2010 and 2011 due to concussion symptoms and other injuries while with the Twins.
The 7-day protocol was created as Morneau was dealing with the aftermath of his 2010 concussion.
"The one thing you don't want to do is put someone in position the day after or two days later all of a sudden by saying, 'Are you feeling OK?' " Morneau said in 2011, according to ESPN. "The worst thing you can do with a concussion is rush back to play. You're diagnosed and you have a week and if it clears up like most people hope it does and they usually do, with most people it's short-term, that's the best-case scenario."
Last season, his first in Colorado, Morneau played in 135 games, hitting .319 with 17 home runs and 82 RBIs.
This season, Morneau has played in 27 games, batting .290 with three home runs and nine RBIs.
Entering Saturday, the Rockies are 12-20 and in last place in the National League West.
- Stanley Kay