It made sense to be optimistic about Northwestern until the middle of August. Trevor Siemian, who threw for over 3,700 yards to go along with 20 touchdowns and 13 interceptions, was returning with key players in Venric Mark and Christian Jones.

Mark rushed for more than 1,350 yards in 2012 before seeing limited action in 2013 due to injuries. Jones grabbed 54 passes for 668 yards and four touchdowns last season.

Then, on Aug. 13, Mark announced he was leaving Northwestern due to personal reasons. Northwestern announced later that day that Jones would miss all of his senior season due to a knee injury.

“Unfortunately for some of our guys, injury going to prevent them to play,” head coach Pat Fitzgerald said Monday. “…I like the way the guys have stepped up and it shows a little bit to our initial depth going into the year but we’ll see how that progresses.”

Even though two of the biggest pieces of the Wildcat’s offense are gone, Siemian spoke at length during Big Ten Media Days in late July about how the team’s offense has the ability to reload.

He didn’t know the losses would happen then, but what the senior said is very applicable roughly a month later.

“It’s probably the most [offensive] depth I’ve seen here since I’ve been around,” Siemian said. “If one guy gets hurt, it’s going to suck, but we have guys all over the place that can pick up the slack.”

Siemian, along with some of those players are being tasked with resurrecting a team that jumped out to a 4-0 start in 2013 but dropped seven of its final eight games — including a 17-10 overtime loss in Kinnick Stadium last October — to finish 5-7 overall with its lone conference win coming in the form of a 37-34 victory at Illinois to end a forgettable season.

Some of the help through the air can come from proven contributors such as Tony Jones and Dan Vitale, who combined for over 1,000 receiving yards and seven touchdowns last season.

Receivers Kyle Prater — who began his career at Southern California — and Rutgers-transfer Myles Shuler can also contribute in Northwestern’s pass-heavy offense.

On the ground, watch for a combination of senior Treyvon Green and freshman Justin Jackson, a two-time Illinois Gatorade Player of the Year in Illinois to carry the load.

On defense, seniors Damien Proby and Chi Chi Ariguzo lead the charge after combining for 218 tackles during last year’s campaign. Much of the talk in surrounding Northwestern is about the speed of their defense.

The Wildcats will have to play a fast brand of football — especially on defense — to keep up with speedy running backs such as Nebraska’s Ameer Abdullah and Wisconsin’s Melvin Gordon.

“Whenever we’re playing seven-on-seven, whenever we’re doing all these different things, I look around — we have some dudes on our team,” linebacker Collin Ellis said. “Our defense is extremely fast, I’m really excited that we’re starting to build some depth.”

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