ARLINGTON — Derek Holland’s return to the Rangers likely won’t occur until late August or early September, a source said Wednesday.An initial plan to send the left-hander out on a rehabilitation assignment to Triple A Round Rock has been revised and pushed back from a targeted July 22 or 23 date.He is expected to make four rehabilitation starts in the minors. Holland, who has been throwing bullpen sessions in recent weeks, said Wednesday he had received no firm word on when he would begin a rehab stint.The lefty has been out all season after surgery on his left knee that was injured while playing with his dog in December.His return has been a subject of speculation all season. At the time of the injury, officials targeted a return in July, though an optimistic Holland vowed a June return.Rehabilitation ultimately has taken longer than expected because the knee has been slow to build stamina and strength.Professor LewisColby Lewis makes his 16th start of the season Thursday against the Angels. While he is seeking a third consecutive quality start, Lewis is also adjusting to his new role of mentor to a makeshift rotation that includes a number of young guys.“We do have a lot of young guys coming in, looking to do well and open eyes,” Lewis said. “They’ll come to me and talk. We’ll go down different scenarios for the game.“You talk to them a little bit and try to get them as relaxed as possible.”Lewis, who went 13 straight starts without a quality start, has had better results of late, he said, because of better command.“When you’re not walking guys, they don’t score,” said Lewis, who is 6-5 with a 5.51 ERA this season. “I’m just trying to stay out of those big innings.”Smolinski moved upJake Smolinski was called up from Triple A on Monday and, with the Rangers facing a left-hander on Wednesday, he was moved up in the order, to fifth.After only a sampling, manager Ron Washington has been impressed, saying Smolinski strikes him as someone who can hit to all fields.Smolinski didn’t have the best start to his big league career, striking out three times in his first four plate appearances.But in his first major league start on Tuesday, he collected the first two hits of his career, including an RBI double.Smolinski had three singles in his first three at-bats Wednesday to collect five consecutive hits.“I hope he continues to progress,” Washington said. “So far, he’s been impressive.” — Brian GossetMartin sitsLeonys Martin was out of the lineup Wednesday because of Houston left-hander Dallas Keuchel.Martin is hitting .200 against lefties and .296 against right-handers.“He’s a guy we expect to play every day, but he’s not hitting lefties well right now,” Washington said.“Coming off the break I’m going to give him some lefties to see if he can figure it out.”Briefly• Washington said Wednesday that Yu Darvish will start the Rangers’ first game after the All-Star break, July 18 at Toronto, regardless of whether he pitches in the midseason classic.• Donnie Murphy rejected an assignment to Triple A Round Rock and has been placed on waivers for the purpose of giving him his unconditional release, a team spokesman said.