The 6-foot-6, 318-pound Newton was a seventh-round draft pick out of Arkansas State in 2011. Butler, entering his sixth season with Houston, was sidelined much of last season with a left triceps injury. Kubiak met with both players on Monday before announcing his decision.
"Looking at the body of work, it was very, very close," Kubiak said. "The thing that moved us toward Newton is watching his progress, watching where he was in the last year, going through the offseason, going through camp -- a young player we think is ascending."
The Texans (No. 4 in the AP Pro32) wrap up the preseason against Minnesota (No. 29) on Thursday night. Kubiak is still mulling whether to play backup quarterback T.J. Yates, who's struggled in the last two exhibition games. Kubiak will also take a close look at veteran quarterback John Beck and rookie Case Keenum, who are competing for the No. 3 spot.
Nose tackle Shaun Cody (back) and defensive end J.J. Watt (dislocated left elbow) returned to practice on Monday, Kubiak said. Linebacker Brian Cushing (bruised ribs) and center Chris Myers (illness) went through individual workouts. Kubiak said star receiver Andre Johnson sat out after coming out of Saturday's 34-27 loss in New Orleans "pretty sore," but "he's fine."
The team also announced that running back Davin Meggett, veteran receiver Bryant Johnson and offensive tackle Nick Mondek were among the players waived as the Texans reduced their roster to the required 75 players.
Center Thomas Austin, linebacker Omar Gaither, punter Brett Hartmann, receiver Mario Louis, defensive end Jimmy Saddler-McQueen, fullback Derrell Smith, guard Kasey Studdard and cornerback Torri Williams were waived.
Meggett, the son of former NFL player Dave Meggett, signed with Houston as an undrafted free agent in May. Johnson, a 9-year NFL veteran, made six catches for 90 yards, including a touchdown, for the Texans last season. Mondek was a sixth-round draft pick out of Purdue.
All teams must trim their rosters to 53 players on Friday.
The competition at right tackle has been one of the most closely watched position battles in Texans camp. The team cut Eric Winston in March, a surprising move after Winston started 88 consecutive games at the position.
Kubiak said Newton showed major improvement late last season.
"He's come a long way from Arkansas State," Kubiak said. "We just see things that give him a chance to be a great player. We've got to get him consistent, and those types of things, but if that was the case, he'd have already been there. There just comes a point where you say, `Hey, we're going to work him through this stuff and he's the best guy for us.' I really like his commitment to what we're doing."
Newton played in 14 games last season and felt like he had a good handle on the Texans' complex playbook by the spring. He was worried about making mistakes in training camp, but got reassurances from teammates.
"Being able to come out every day and try to make each play good, it's hard," Newton said. "I had a lot of guys come up to me and tell me, `Just take it one play at a time, be calm and you'll be all right."'
Kubiak revealed on Sunday that rookie kicker Randy Bullock would miss the season with a torn muscle near his groin, solving another of the tight position duels in training camp. That leaves the job to 34-year-old Shayne Graham, who's 5-for-5 on field goals in the preseason, including a 53-yarder.
"Shayne's had a heck of a camp," Kubiak said. "To sit here and say Shayne might've won the job anyway, I don't know. We had another week to go, but they were both kicking extremely well. But I've got a lot of confidence in him, he's earned his keep around here."
Also Monday, the Texans placed linebacker Darryl Sharpton on the Physically Unable to Perform (PUP) list with a right quadriceps injury. The team also announced that nose tackle Ra'Shon Harris (right triceps) and linebacker Greg Williams (hamstring) were waived/injured.