Kenneth Dixon's biggest challenge is proving he can stay on the field

OWINGS MILLS, Md. -- Baltimore Ravens coach John Harbaugh said this offseason that he believes Kenneth Dixon is "going to be a really good back in this league."

That is, if Dixon can remain on the field.

Dixon's knee surgery on Tuesday is the latest reminder that he has a ways to go before the Ravens can count on him being a featured running back. Since being drafted in the fourth round 15 months ago, Dixon has dealt with three knee injuries, a strained hamstring, a chest contusion and a four-game suspension.

As a rookie, Dixon showed flashes of being a playmaker. He's elusive. He can break tackles.

Over the final eight games last season, Dixon ranked fourth among rookie running backs with 515 yards from scrimmage. Only Dallas' Ezekiel Elliott, Chicago's Jordan Howard and Washington's Rob Kelley produced more.

It appeared as if 2017 was all set up for Dixon to take over the lead role in the Ravens' backfield. Terrance West has averaged 3.9 yards per carry in his career. Buck Allen has disappeared after being inactive for the final five games last season. And Lorenzo Taliaferro has been moved to fullback.

But Dixon's first setback of the year came in early March, when he was suspended for the first four games of the regular season for violating the NFL's policy on performance-enhancing drugs. This offseason, Dixon said it was going to be "difficult" to be out until Week 5.

"It is just something that I have to deal with," Dixon said. "I have talked about it with my family, my friends, my teammates, my coaches, and we are ready to get past it, so we can get ready for Game 5. I am working really hard to come back strong."

Coming back strong is going to be a challenge for Dixon. His knee surgery this week extends a bad trend.

Last year, he missed rookie minicamp and the first month of offseason workouts with a hamstring injury. He was also sidelined early in training camp last year with a strained MCL in his left knee.

Then, Dixon had to sit out the first four games in 2016 after spraining the MCL in the same knee. A month after returning, he had to leave a game against the Steelers after suffering a bruised chest.

Dixon can be a key component in jump-starting a Baltimore running game that ranked No. 28 in the NFL last season. He was rated the second-most elusive back in the NFL last season by Pro Football Focus. In the final eight games, Dixon forced 32 missed tackles, which ranked third most by a running back in that span despite 26 other players having more touches.

"I think he’s going to be a really good player," Harbaugh said in March. "He wants to be good. He made a mistake [four-game suspension]. Not a mistake that he's very proud of. But I think he’s going to put it behind him, and he's going to be a really good back in this league."

But the only way he can be a really good back is if he can make the Ravens believe he will be there on the field when the team needs him.