Gurley signed a 4-year, $57.5 MILLION contract before last season -- and was the team's workhorse ... averaging 18.3 carries per game plus 4.2 catches per game.

But, this year ... he's been rotated in and out of the lineup for backup Malcolm Brown -- and has seen his touches drop to just 12.2 carries per game and 2.8 catches per game.

Bruce says TG's role in the offense so far is perplexing ... telling us, "It's strange to see with Todd being as young as he is being on somewhat of a management program."

Bruce added, "It's kind of strange. It's different."

If it were up to Isaac, the Rams legend would be feeding Gurley nonstop ... because he says when RBs were running well during his playing days -- it opened up EVERYTHING for him in the secondary.

"If you get that guy -- and get that group -- running; bring that safety down, it benefits everybody."

As for the Rams' pivotal game against the Seahawks on Thursday night ... he ain't so sure who's coming out with the W -- telling us both squads are the easy favorites to win the NFC West this year.