Lee, one of the biggest potential chips at the trading deadline, was limited to just 24 pitches for Class-A Clearwater on Sunday when the game was suspended. He had planned on throwing 70 piches.
Phillies general manager Ruben Amaro Jr. told the Philadelphia Inquirer that Lee's fastball was clocked between 89 mph and 91 mph.
"We liked what we saw of his two innings," Amaro said.
The 35-year-old Lee will make two more rehab starts and now is targeting July 19 for his return from the disabled list. The trade deadline is July 31.
The left-hander hasn't pitched since complaining of elbow soreness after throwing 116 pitches in a May 18 start against the Cincinnati Reds. The injury was originally described as a mild strain of the flexor pronator muscle in his left elbow.
If the Phillies are out of contention at the trading deadline, they are expected to listen to offers for many of their veteran players. But other clubs have told ESPN.com that they expect the Phillies to aggressively attempt to move Lee, who is signed through 2015 and has a minimum of $50 million left on his contract over the next season and a half. That figure could grow to $62.5 million if he vests his option for 2016.
Teams that have spoken with the Phillies say the club has indicated it is willing to eat a significant portion of Lee's salary if it gets the right pieces back in a trade.
Lee was 4-4 with a 3.18 ERA in 10 starts before going on the disabled list. In the six starts in which he received a loss or a no-decision, the Phillies scored a total of eight runs while he was in the game.
Jayson Stark of ESPN.com contributed to this report.