Houston — The more Ty Johnson's speed shows up on the practice field, the more difficult it is to understand how he fell to the sixth-round of the NFL Draft. After all, this is a guy who averaged 7.6 yards per carry during his four years at Maryland, while flashing some real ability as a return man, as well.

For whatever reason evaluators slept on the 5-foot-10, 210-pound running back, it's looking like Detroit Lions general manager Bob Quinn and the team's college scouting staff may have unearthed a gem.

"You see on tape, you see some of the physical attributes that you really like, that I think have shown up on the field so far," Lions coach Matt Patricia said. "That’s always a positive to see. Again, there’s a difference between the level of play and competition between college and the NFL. You always try to project that at our level, and I think that’s part of it that’s shown up on the field.”

Johnson didn't get a lot of playing time in college, which likely contributed to anchoring his stock. He noted that Maryland leaned heavily on a rotation of backs, but following the advice of his mother, he always made the most of each of his 348 college carries.

Johnson also credited Maryland's scheme and the blocking of his offensive linemen for his success. In Detroit, he's focused on maintaining the attitude of making the most of each opportunity, learning the scheme and following the blocks he's provided.

That showed up during the first of two joint practices with the Texans on Wednesday, when he shot through the heart of the line for a 15-yard touchdown run.

Shot being the key word, because Johnson's speed is eye-catching.

"Coach Leon (Washington) always says this game is all about speed and I've got a lot of speed, he says," Johnson said. "So every chance I get to open up, I open it up. It's like having a muscle car going down the highway, you've got to open it up a little bit."

Taking the muscle car analogy further, Johnson said the key to porting his speed advantage to the NFL, where defenders are far faster, is about maintenance. With a car, you need to change the oil and tires, to get peak performance. For him, it's about putting in extra work in the weight room.

In the preseason opener, Johnson rushed for 22 yards on three carries, including a long of 17. He had another 13-yard run called back by a holding penalty. He was part of a select group of performances Patricia highlighted as positives out of the games.

The Lions clearly believe they have something in Johnson, enough that they were comfortable moving on from veteran Theo Riddick, the team's best third-down back the past three years.

Johnson will look to continue his momentum in Detroit's second preseason game, Saturday night against the Texans.