Tampa Bay Buccaneers quarterback Josh McCown (12) eludes St. Louis Rams E.J. Gaines (33) and outside linebacker Alec Ogletree on a 5-yard touchdown run during the first quarter of an NFL football game Sunday, Sept. 14, 2014, in Tampa, Fla. (AP Photo/Brian Blanco)

St. Louis Rams running back Zac Stacy (30) celebrates with teammates, including tight end Lance Kendricks (88) and center Tim Barnes (61), after scoring against the Tampa Bay Buccaneers during the first quarter of an NFL football game Sunday, Sept. 14, 2014, in Tampa, Fla. (AP Photo/Brian Blanco)

St. Louis Rams running back Zac Stacy, left, dives over for a touchdown on a 2-yard run during the first quarter of an NFL football game against the Tampa Bay Buccaneers on Sunday, Sept. 14, 2014, in Tampa, Fla. (AP Photo/Brian Blanco)

St. Louis Rams quarterback Austin Davis (9) tries to escape the grasp of Tampa Bay Buccaneers defensive end William Gholston (92) during the first quarter of an NFL football game Sunday, Sept. 14, 2014, in Tampa, Fla. (AP Photo/Brian Blanco)

St. Louis Rams quarterback Austin Davis (9) is sacked by Tampa Bay Buccaneers defensive tackle Clinton McDonald (98) during the third quarter of an NFL football game Sunday, Sept. 14, 2014, in Tampa, Fla. (AP Photo/Phelan M. Ebenhack)

St. Louis Rams kicker Greg Zuerlein (4) follows through on his field goal as Tampa Bay Buccaneers cornerback Johnthan Banks (27) attempts to block it during the fourth quarter of an NFL football game Sunday, Sept. 14, 2014, in Tampa, Fla. The Rams won the game 19-17. (AP Photo/Chris O'Meara)

Rainey, who was a useful fantasy runner for part of last season, is again playing a bigger role with Doug Martin (knee) out of action. He thrived against the Rams, rushing for 144 yards. With a short week ahead (the Buccaneers face the Atlanta Falcons on Thursday Night Football), Martin is no lock to be back in the lineup for Week 3. Such a scenario would make Rainey a legitimate flex starter for owners.