The Giants had planned to work out McGahee since Friday, according to the source.
Former New York Jets running back Joe McKnight also will work out for the Giants on Tuesday, sources confirmed to ESPN.
Jacobs tweeted about the workout on Monday.
Jacobs, 31, spent his first seven seasons with the Giants before struggling through an injury-plagued season with the San Francisco 49ers in 2012. San Francisco waived Jacobs in December after the outspoken veteran was suspended for the final three regular-season games reportedly because he used social media to complain about a lack of playing time.
McGahee, who will turn 32 next month, was released by the Denver Broncos in June following a productive 2012 season that was cut short by a significant knee injury. Despite not participating in Denver’s voluntary offseason workouts, McGahee insisted that he had no physical restrictions when he was released.
Jacobs rushed for 56 touchdowns in his seven seasons with the Giants and was a key contributor on New York’s two Super Bowl-winning teams under coach Tom Coughlin.
McGahee rushed for 731 yards and four touchdowns in 10 games with Denver last season. The two-time Pro Bowler has 8,097 rushing yards and 63 touchdowns over parts of nine seasons with the Broncos, Baltimore Ravens and Buffalo Bills.
If either veteran signs with the Giants, he would provide much-needed depth to a New York backfield that has been beset by injuries and inconsistent play over the past three weeks.
Giants starter David Wilson was benched during Sunday’s season-opening loss to the Dallas Cowboys after fumbling twice and struggling in pass protection. Coughlin indicated that Wilson would have a chance to reclaim the starting job.
“Give us a little time to work on this thing,” Coughlin said Sunday. “[Wilson] is still very much in our thoughts. He’s got to play — he’s a very talented young man.
“But you just can’t do that. Every time they touch you, you’re going to turn the ball over?”
The Giants also will be without veteran running back Andre Brown, who is on temporary injured reserve after suffering a fractured leg in the preseason finale. Brown, who rushed for eight touchdowns last season, will not be eligible to play until Week 9.
Da’Rel Scott, who replaced Wilson on Sunday, and rookie Michael Cox are the only other running backs on New York’s roster.
Information from ESPNNewYork.com’s Ohm Youngmisuk and The Associated Press was used in this report.
This article was originally posted on ESPN.com