It's still unclear who the Eagles starting quarterback will be in 2015. Reports indicate that the Eagles are going to make a strong play for Marcus Mariota, but it's far from guaranteed that Philadelphia will be able to draft Chip Kelly's former Oregon quarterback. Meanwhile, Nick Foles is entering the final year of his rookie deal.

But while the starting quarterback is the main focus, it's also unclear who the backup might be. The Eagles and Mark Sanchez reportedly have mutual interest in getting back together, but the Eagles could explore other options on the free agent market.

According to CSN Philly's Geoff Mosher, the Eagles are interested in a few veteran passers on the market. The first name Mosher mentions is former first round pick Tarvaris Jackson. The 31-year-old veteran made his NFL debut in 2006 with the Minnesota Vikings. Most recently he's spent the past two seasons as the backup to Seattle Seahawks quarterback Russell Wilson.

Jackson is 17-17 as a starter in his career. He's attempted 1,067 passes for 636 completions (59.6%), 7,226 yards (6.8 average), 39 touchdowns, 35 interceptions, and a 78.5 passer rating. Jackson has proven to be mobile with 644 career rushing yards.

Another free agent quarterback possibility for the Eagles mentioned by Mosher is Jake Locker. The Eagles have already been rumored to be interested in him. The former No. 8 overall pick isn't expected to return to the Tennessee Titans. Locker is only 26 and could be viewed as a reclamation project, though he would likely be a backup. Locker is a good athlete but he's struggled to stay healthy.

Lastly, Mosher notes that the Eagles are not expected to have interest in free agent quarterback Josh Johnson.

It's interesting to think what these backup quarterback plans could mean for what the Eagles could do at the starting position. On one hand it could be argued Chip Kelly is looking for a veteran backup to fall back on if Nick Foles struggles again and/or gets hurt. On the other hand, having an experienced veteran around could be good for a young quarterback like Marcus Mariota.

One more interesting note from Mosher is that the Eagles haven't discussed the long-term future with Foles yet.

"According to a source close to the situation, Kelly hasn’t yet discussed Nick Foles’ long-term future with the fourth-year quarterback. Now that Foles has accrued three NFL seasons he’s eligible for an extension but there are no indications that Kelly plans to move forward with the quarterback who has won 14 of the 18 games he’s started under Kelly."