Houston Texans running back Arian Foster has admitted that it has been a difficult time for him recovering from consecutive calf and back injuries.

Foster, who carried 18 times in training on Monday, said that waiting to play a big role once more was the reason for his frustration in the season opener against the San Diego Chargers.

"They had a gameplan going in about how much they wanted me to play and they were trying to ease me back into it, but my competitive nature, of course you want to be in," Foster told ESPN.

"It's getting to crunch time, it's the fourth quarter and you want to be out there. But this is kind of how it played out. In my opinion, you would be concerned with a player that's happy he's not in there in the last minutes of the game when the game is on the line."

Foster's injuries kept him out for the majority of pre-season.