Courtney Lee headed to Celtics?

The Boston Celtics are close to acquiring free-agent shooting guard Courtney Lee in a sign-and-trade deal with the Houston Rockets, according to a league source.

The Celtics are expected to send out JaJuan Johnson, E'Twaun Moore, Sean Williams and a second-round pick in exchange for Lee, although it's still possible the pieces could change as the sides work to finalize the trade.

With those combined contracts, Boston could absorb as much as $4.25 million in the first year of a contract for Lee. Yahoo! Sports reported Lee landed a four-year, $21.5 million fully guaranteed deal from the Celtics in the sign and trade.

After losing Ray Allen to the Miami Heat and with Avery Bradley potentially sidelined for the start of the 2012-13 season after undergoing a pair of shoulder surgeries, the Celtics were in need of a front-line shooting guard. Lee would fill that role, allowing Jason Terry -- who was officially signed Wednesday for the mid-level exception -- to stay in his preferred sixth-man role.

Lee averaged 11.4 points in 30.3 minutes per game last season and shot 40.1 percent beyond the 3-point arc in 58 appearances, including 26 starts.

The Celtics attempted to engage the Dallas Mavericks in a sign-and-trade deal for Terry that would have allowed them to use the mid-level to lure Lee. When that failed, Boston pushed harder with Houston to work out the deal.

Boston likely will send out last year's first-round pick (Johnson) and a pair of non-guaranteed contracts (Moore and Williams). For helping to facilitate the deal, the Rockets would get another draft pick for their stockpile.

Johnson, Moore and Williams all were absent from the Celtics' summer league game in Las Vegas against the Sacramento Kings on Thursday.

Johnson was never seen in the arena, while Moore and Williams arrived with the team but eventually left the floor during warm-ups. Moore and Williams each shared a one-on-one conversation with Celtics coach Doc Rivers in the tunnel next to Boston's locker room before departing the arena.

Rivers and Celtics president of basketball operations Danny Ainge are in Las Vegas taking in summer league action, but both declined to comment on any reports concerning Lee.

Information from ESPNBoston.com's Greg Payne was used in this report.