New Lakers Josh McRoberts, Troy Murphy make an impact in opener

Josh McRoberts was doing his McRambis thing, bulling others out of the way for rebounds, chasing loose balls and even showing some offensive might with a couple of dunks.

Troy Murphy had his moments too, batting balls to teammates and burying a baseline jumper early in the fourth quarter a tick before the shot clock expired.

The Lakers post players who filled in for the suspended Andrew Bynum came up big for much of their team’s opener Sunday at Staples Center until a disastrous stretch over the final two minutes left them feeling two inches tall.

McRoberts missed two free throws with 1 minute 12 seconds left, part of a Lakers collapse in which they squandered a six-point lead in the final 50 seconds of their 88-87 loss to the Chicago Bulls.

“Christmas got canceled,” McRoberts said. “I’ve got to get better at basketball. I’ve got to learn the offense.”

He’ll have more opportunities in the coming days. Sunday marked the first game in which McRoberts and Murphy will play increased roles while Bynum serves a four-game suspension for committing a flagrant foul in last season’s playoffs.

With Bynum out, Pau Gasol has shifted to center and McRoberts has become the starting power forward, with Murphy the only big man off the bench.

McRoberts had six points, eight rebounds and two blocks in a debut Lakers guard Kobe Bryant described as “terrific.” The hustle player nicknamed “McRambis” by some fans powered his way into the lane in the second quarter for a two-handed dunk and shortly afterward fed Bryant for a layup.

There were also some things that went awry for the 6-foot-10 forward who wore his socks nearly up to his knees — including a length-of-the-court pass over Gasol’s fingertips and those late missed free throws.

“If they would have paused it in the middle of the shots,” McRoberts said, “I said I would have bet anything they were going in. Both of them felt good.”

Murphy made three of five shots on the way to collecting seven points and eight rebounds in 22 minutes. Like McRoberts, the 6-11 Murphy joined training camp late after signing with the Lakers shortly before the season, which has complicated the transition.

“I’m still trying to find my way with the offense and find the correct spots that I’m supposed to be in,” Murphy said, “so it’s a work in progress.”

McRoberts and Murphy are already familiar with each other. They were teammates for two years with Indianapolis, most recently during the 2009-10 season, before their careers took divergent paths. McRoberts averaged a career-high 7.4 points with the Pacers last season while Murphy averaged a career-low 3.1 points in only 35 games with two teams.

Now they’re together in a place where things like McRoberts’ sock length gets noticed.

“I’m not used to this,” McRoberts said. “I’m used to being in Indiana where no one really pays attention, but this is a whole different thing.”

ben.bolch@latimes.com