PISCATAWAY -- Rutgers started spring camp short-handed at quarterback ... and now is down to just four hands.

Redshirt senior Zach Allen suffered a torn ACL during Saturday's practice and is sidelined for an undetermined amount of time, coach Chris Ash announced. He did not practice Tuesday or Thursday and figures to miss at least the start of the season.

That leaves Rutgers with just two quarterbacks available for the spring game: Returning starter Giovanni Rescigno and walk-on Troy Anthony.

"We're not sure what direction Zach will go," Ash said. "He's still visiting with trainers and doctors about what the next step is but he will not participate in the spring game."

The spring pecking order already was settled -- Allen was No. 2 on the depth chart -- but the real competition to be the starter begins in June when St. Peter's Prep star Johnathan Lewis arrives with the rest of the 2017 recruiting class.

Rescigno and Lewis figure to be No. 1 and No. 2 in either order once the season begins, with Allen penciled in as the scholarship No. 3 option for depth.

Allen transferred to Rutgers as a graduate from TCU with two years of eligibility remaining. He completed 1-of-12 passes in two games as a backup but was bypassed when Rescigno took over for the struggling Chris Laviano.

The Texas native said he never considered not returning to Rutgers, which parted ways with transfers Laviano, Hayden Rettig and Mike Dare in the offseason. He is pursuing a graduate degree in labor relations.

"I don't know why I wouldn't come back," Allen said at the start of spring camp. "I really enjoyed it here last year even though the season didn't go the way I wanted it. That's why you move past one year and you move on to the next. I'm looking forward to this year."

The injury, which happened during quarterback run drills, magnifies the impact of Ash dismissing sophomore quarterback Tylin Oden earlier this month for a violation of team rules.

The three-star 2016 recruit, who struggled in five games last season, was thought to be the future of the program at this time last year.

It is unclear what's next for the dual-threat Allen, who needs to be mobile to have a chance to succeed.

If Allen undergoes surgery, he could be put on a college career-ending medical scholarship. Or he could try to pursue a NCAA waiver for a rare sixth year of eligibility in 2018.

Or Allen could elect to skip surgery and try to rehabilitate his knee in time to get back on the field in 2017. That's the road that Ash initially took as a senior with a torn ACL as a player at Drake University.

"There are several options that we'll take a look at," Ash said. "A lot of it is going to be based on Zach and his family. We want Zach to do what's best for him. Zach is a very intelligent young man and he is going to have a successful career when football is over. He just has to figure out what's next right now: What can we do to potentially get him back and help us in some capacity next fall?"

At the time of Oden's dismissal, Ash said that Rutgers was not in the market for a graduate transfer quarterback -- and had no scholarship room to add one.

Should Allen be placed on medical scholarship -- or if players transfer after spring camp as is the norm across the nation -- availability could change.

But that doesn't mean that Rutgers will go that route for a No. 3 quarterback.

"We are going to explore all options," Ash said. "It doesn't mean we are going to necessarily going to go do that route. But we definitely have to go look at all the options that are potentially available."

Ash added two walk-on quarterbacks in recent weeks in an attempt to build depth that suddenly is needed -- especially to manage practice.

Temple transfer Tommy Wyatt, who was recruited by Ash soon after he arrived at Rutgers, joins the fold next season with four years of eligibility remaining. So does Southern Connecticut State's Rob Nittolo, an immediately eligible graduate transfer who can play two seasons.

It's been a difficult camp for short-handed Rutgers, which lost promising redshirt freshman wide receiver Ahmir Mitchell to a torn ACL. He underwent surgery last week and is out until at least the start of Big Ten play on Sept. 23, though it remains possible he could miss the entire season.

All ACL injuries require different recovery times between 6-12 months, though 8-10 is common.

Ryan Dunleavy may be reached at rdunleavy@njadvancemedia.com. Follow him on Twitter @rydunleavy. Find NJ.com Rutgers Football on Facebook.