Waller -- who played with Taliaferro in Baltimore to begin his career -- scored on a beautiful 35-yard, go route early in the 2nd quarter of the Raiders' loss to the Chargers ... and he immediately got up and looked for cameras in the end zone.

DW then threw up a 3 and a 4 -- Taliaferro's old jersey number -- and then he gave a bow.

In the pregame, Waller also wrote a note to Taliaferro on his cleats ... putting in pen, "R.I.P. Zobot #34."

"To be real, I didn't even feel like playing tonight honestly," Waller said after the game. "I had no juice today. I thank God and the people that support me for speaking life into me today, and telling me to go out and play and represent him and to have him on my mind while I was playing."

"I feel like him and his presence and what his time on the earth meant to me is what motivating me to play football with a sense of urgency."

Taliaferro tragically died in Virginia on Wednesday ... a family member told Fox45 in Baltimore the former running back had suffered a heart attack.

Waller -- who finished Thursday night with a staggering 150 yards on 9 catches -- was teammates with the ex-Raven from 2015 to 2017.