WASHINGTON -- The Nationals have placed first baseman Dmitri Young on the 15-day disabled list with a lower back sprain and activated catcher Johnny Estrada from the DL.

Young has been bothered by tightness in his back since Spring Training, but played through it until last Thursday when he wasn't available to pinch hit against the Phillies. Young subsequently received a cortisone shot, but his back didn't get any better. The Nationals were hoping Young would work out on Wednesday, but he didn't feel any better on Tuesday.

For the season, Young is 1-for-2 with an RBI.

Estrada started the season on the DL because of a sore elbow. He started a rehab assignment recently and went 4-for-12 (.333) with an RBI for Triple-A Columbus.

Right now, the Nationals have three catchers on their roster, including Paul Lo Duca and Jesus Flores, who will reportedly be sent down to Double-A Harrisburg when Estrada is activated.

General manager Jim Bowden wasn't available for comment.