The Rangers and Red Sox reached a preliminary agreement Wednesday on a deal for Lowell that would send minor league catcher Max Ramirez to Boston, with the Red Sox picking up $9 million of Lowell's $12 million salary for next season.
The Globe reported the Rangers had signed off on the condition of Lowell's surgically repaired right hip but were continuing to examine his right thumb.
"There are still things to go over," Red Sox assistant general manager Ben Cherington said Saturday, according to the Boston newspaper.
The Rangers are expected to conduct a physical with Lowell this week, a major league source told ESPNDallas.com's Richard Durrett.
Another issue thought to be holding up the deal was the approval of the commissioner's office, which must OK a cash swap of that size. The Globe reported Bud Selig had yet to receive the necessary paperwork as of Saturday.
"It would not be a complete surprise if it didn't happen," Cherington said.
Rangers general manager Jon Daniels would not comment on the pending deal when contacted Sunday morning by ESPNDallas.com.
The 35-year-old Lowell was an All-Star four times from 2002-07, hitting .324 with 21 homers and 120 RBIs in 2007. But he slumped to 73 RBIs in 2008 and 75 RBIs this year, hitting 17 homers each season.
Lowell had surgery in October 2008 to repair a torn labrum in his right hip and remove a bone spur on a thigh bone. He will be entering the final season of a $37.5 million, three-year contract.
Daniels said Thursday morning that both teams still had the option of walking away from the deal, but other club executives said it was their understanding the deal would move forward.
Information from ESPNDallas.com's Richard Durrett and ESPNBoston.com's Gordon Edes was used in this report.