TEMPE, Ariz. -- With Tuesday’s news that Arizona Cardinals running back Chris Johnson was put on injured reserve/designated to return, which means the earliest he’ll be eligible to play will be Super Bowl 50, rookie David Johnson was thrust into a larger role.

He could find himself starting his weekend in St. Louis if backup running back Andre Ellington is out with a turf-toe injury. Johnson has rushed for 139 yards and four touchdowns on 35 carries this season, while catching three touchdowns and returning one more.

Here are five things to know about the Cardinals’ third-round pick:

• Johnson spent his offseasons in college working for the school’s maintenance department, unclogging drains and cleaning toilets.

• He is part of a set of triplets, along with sisters Darnecia and Danielle.

• He leads all rookie running backs and receivers with eight total touchdowns -- four rushing, three receiving and one return touchdown.

• He’s the first player in NFL history to score touchdowns by run, pass and kick return in his first two games.

• Johnson’s 108-yard return on the opening kickoff of Week 2 against the Chicago Bears was the longest touchdown in Cardinals history and tied for the second-longest in NFL history.