Cavs' Jarrett Jack headed to Nets

— -- The Cleveland Cavaliers will trade Jarrett Jack to the Brooklyn Nets on Thursday as part of a three-team deal with Boston to create more salary-cap space for the pursuit of LeBron James, according to sources close to the process.

Sources told ESPN.com that the Nets have agreed to take on the contracts of Jack and youngster Sergey Karasev from the Cavaliers in a swap that also will see the Celtics acquire Brooklyn's Marcus Thornton, Cleveland's Tyler Zeller and a future first-round pick from the Cavaliers.

Cleveland will have to acquire at least one future second-rounder from either Brooklyn or Boston to complete the transaction, but the moves will give the Cavaliers significant financial flexibility, shedding Jack, Zeller and Karasev from their roster.

Meanwhile, ESPN The Magazine's Chris Broussard reports that the Cavaliers, in addition to James, are also now trying to strike a deal with free agent guard  Ray Allen as a means of enticing James even more about a return to Cleveland. 

After briefly considering retirement following the Heat's loss to the Spurs in the NBA Finals, Allen is leaning toward returning for a 19th season, sources said.

According to ESPN's Tom Penn, the trade of Jack sheds $9.5 million in salary (Jack, $6.3 million; Zeller, $1.7 million; Karasev, $1.5 million), giving the Cavaliers $21.7 million in cap space.

The trade can't be officially consummated until Thursday, when a league-wide moratorium on signings and trades is lifted at 12:01 a.m.