Allen missed practice the previous two days because of an ailing right knee. On Thursday, Chargers coach Anthony Lynn told reporters he was unsure of Allen's chances of playing Sunday.
"We'll see. Not sure," said Lynn. "That knee was really sore yesterday."
Allen is tied for the team lead with 17 receptions for 219 yards and a touchdown. He had a season-low three catches for 44 yards in last weekend's 35-23 loss at the Los Angeles Rams.
The sixth-year wideout played in 16 games last season, making 15 starts, and set career highs with 102 receptions for 1,393 yards. He also had six touchdowns in earning his first Pro Bowl berth.
A third-round draft pick of the Chargers in 2013, Allen notched at least 67 receptions in each of his first three seasons and scored a career-high eight touchdowns in his rookie campaign.
Allen has dealt with two major injuries that derailed half of one season and almost all of another.
In 2015, Allen had 67 receptions in eight games before his season ended due to a kidney injury.
Allen then suffered a torn ACL, also in the right knee, in the 2016 season opener, but he came back to play in all 16 games for the first time in his career in 2017.