It's because Lancashire's Matt Parkinson has been ruled out of the Lions tour of the UAE after routine scans found a stress fracture in his back.
The leg-spinner was the highest wicket-taker in the 2018 Royal London One-Day cup, taking 18 wickets, and the second-highest wicket-taker in the 2018 Vitality Blast, with 25. He took 59 wickets across all three formats.
Parkinson will be replaced in the England Lions squad by Sussex slow left-armer Briggs, who has played eight internationals for the full England side, last appearing in 2014.
Coach Andy Flower said: "It's a real shame for Matt that he's forced to miss the tour. He had a fine summer for Lancashire and his selection was just reward for the ability that he's shown.
"He's been shut down from bowling and he'll see a spinal specialist this week as we try to determine the full extent of his injury.
"It does provide an opportunity for Danny to demonstrate what he can do. He's a proven performer at county level and, like Matt, he had an impressive summer across all forms of the game."
November 18-21: Four-day match v Pakistan A, Abu Dhabi
November 25: First 50-over match v Pakistan A, Dubai
November 27: Second 50-over match v Pakistan A, Dubai
November 29: Third 50-over match v Pakistan A, Abu Dhabi
December 2: Fourth 50-over match v Pakistan A, Abu Dhabi
December 5: Fifth 50-over match v Pakistan A, Dubai
December 7: First T20 v Pakistan A, Abu Dhabi
December 8: Second T20 v Pakistan A, Abu Dhabi