The Astros also signed lefty reliever Tim Byrdak to a one-year deal worth $1 million.
Backe, who struggled down the stretch in 2008, his first full season after undergoing Tommy John elbow ligament replacement surgery, can earn up to $825,000 in bonuses as a starter. The contract also calls for an incentive package as a reliever, but only as a backup plan. Backe will compete for the fifth-starter job during Spring Training.
The incentive breakdown is based on innings pitched. He'll earn an extra $50,000 for reaching 160 innings, $100,000 for 170 innings, $150,000 for 180 innings and $175,000 for 190, 200 and 220 innings.
Tuesday was the deadline for teams and players to file salary figures for 2009. The Astros are still negotiating with right-hander Geoff Geary and left-hander Wandy Rodriguez, the club's two remaining arbitration-eligible players.
Geary submitted a proposed salary figure of $2.1 million; the Astros countered with $1.425 million. Rodriguez is asking for $3 million against Astros' proposed $2.25 million.
Arbitration hearings begin Feb. 1 and run through Feb. 21.
Alyson Footer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.