ARLINGTON -- Conor Jackson received a day off Saturday, though it may not have felt much like it.

Jackson, entered as a defensive substitution in the sixth inning and doubled in the eighth for his first hit in 19 at-bats, avoiding tying a career-worst stretch. But Jackson was involved in a collision with Elvis Andrus at first base in the ninth inning and was visited by team trainers but remained in the game.

Manager Bob Melvin said before the game that it was time for Jackson to get some time off. He hadn't hit for much power -- Jackson cracked his second homer on Sunday to end a 49-game drought -- and he had only 22 RBIs in 69 games. Jackson has driven in at least 75 runs twice in his career.

"He's just trying a little too hard right now," Melvin said. "He's been up in some situations where there's been some runners on base, and in the past that's where he's really thrived is in RBI situations. To an extent, he's struggling a little bit and everybody goes through it during the course of a season."

Melvin, Jackson's manager for five seasons in Arizona from 2005-09, said it's more a mental thing than a physical one for the outfielder.

"He keeps himself in great shape," Melvin said. "He's ready to play every day, but sometimes it's just a little bit of a mental grind for a guy that's used to driving in some runs. Recently, he has been in a little bit of a funk offensively."

Sizemore showing he belongs in big leagues

ARLINGTON -- Scott Sizemore has been a pleasant surprise for the A's since taking over at third base after he was called up from Triple-A Sacramento on June 6.

Sizemore, who primarily played second base with the Tigers, has improved steadily at third. More important, he's hit well while learning a new position and made a nice play in a 7-6 loss on Saturday when he leaped into the stands to snare a foul ball.

Sizemore finished Saturday with 10 hits in his past 32 at-bats. He had three home runs, six RBIs and four multi-hit games, as he flashed the offensive ability that made him a heralded prospect in the Tigers' system.

Sizemore, who was traded from the Tigers to the A's on May 27, is learning where to position himself at third, manager Bob Melvin said.

"The more comfortable he gets, there more entrenched he'll get there," Melvin said. "It's difficult to give him a day off because he's been an offensive force for us. Now, he's hitting in the middle of the lineup. He's gone from the new guy here, not sure he'd be able to play the position, to a guy we count on every day."

Looking for swing, Carter gets another start

ARLINGTON -- Chris Carter was in the A's lineup for the eighth time in 10 games Saturday against the Rangers and continues to adjust to Major League pitching, though he exited in the sixth inning in favor of a defensive substitution.

Carter finished the day with four hits in his 28 at-bats this season and he has struck out in nine consecutive games. He had 13 strikeouts, fanning almost half the time. The 6-foot-4, 244-pound first baseman said it has been an adjustment since being called up on June 23 from Triple-A Sacramento.

"I'm still trying to find my swing," Carter said, "and trying to get used to things."

A's manager Bob Melvin, who took over as manager just before Carter arrived, sees a lot of potential in the 24-year-old.

"The ability is there," Melvin said. "It's more about him just getting comfortable, having some results, having some success and building off of that."

Worth noting

• Josh Willingham was the A's designated hitter for the third straight game after coming off the disabled list, but manager Bob Melvin said the outfielder is doing fine physically. Willingham will start in left field on Sunday.

• Melvin played with Derek Jeter for Triple-A Columbus in 1995 before the current captain of the Yankees reached the Majors. Melvin said Saturday it was no surprise that the All-Star shortstop notched his 3,000th hit in dramatic fashion with a home run.

"He did it in typical Jeter fashion," Melvin said. "He embodies that winning type of player."

• The A's committed their 71st error on Saturday, the second most in the American League to their current opponent, the Rangers, who have made 72.