After setting a career high in home runs this past summer, Astros prospect Koby Clemens is still determined to prove he's the real deal.

Clemens hit one of three longballs to highlight a four-run rally and fuel the Peoria Javelinas' 6-4 win at Mesa on Thursday in the Arizona Fall League.

"It's been great. I'm seeing good pitching. There's a lot of good players here and we're all trying to show what we have to offer," Clemens said. "It's been a blast, the weather has been awesome, so it's been unbelievable. It's been a great experience."

The 2009 California League Player of the Year ripped his two-out homer in the sixth, his second in three games. He finished 1-for-3 with a walk and a stolen base. The Astros prospect, who went deep Tuesday, has driven in a run in each of his last three games and has seven RBIs in nine games.

The game turned in the sixth when the Phillies' B.J. Rosenberg replaced Aaron Pribanic (Pirates) for Mesa and nearly surrendered three consecutive homers. Rosenberg started the frame by walking Ryan Lavarnway (Red Sox). He popped up Eric Thames (Blue Jays), but Red Sox outfielder Juan Carlos Linares followed with a two-run homer to left for a 3-1 lead. Rosenberg got Indians infielder Jason Kipnis to pop up, but Clemens and Matt Lawson (Mariners) followed with back-to-back homers to cap the rally.

"We had a nice inning," Clemens laughed. "I came up, and he went ahead 1-2, so I was just thinking about hitting something hard. He left it in a good area where I could get a piece of it and got enough to get it out of the park."

Clemens said he watched Rosenberg from the on-deck circle to get an idea of what he'd face.

"I was trying to see what he had. When I got on deck, I was trying to time it up best I could and kinda react when I got in there," he said. "Just not trying to do too much at the plate."

Houston sent the first baseman to Arizona after he set a personal best with 26 homers at Double-A Corpus Christi in 2010. He posted huge numbers a year earlier when he won the California League batting title by hitting .341 and knocking in 123 runs in 121 games at two levels.

Clemens, whose numbers dipped from his breakout campaign, finished the year batting .241 with 85 RBIs and a .350 on-base percentage in the Texas League. His year was highlighted by an All-Star selection in which he hit off his seven-time Cy Young Award-winning father, Roger, in the league's Home Run Derby.

He said his dad has already made a trip out to watch him play this fall.

"He was out here for the opening week," Clemens said. "But I don't know when he'll make it back. He was here for the first few games, though."

Clemens has done plenty in the Minors with his bat to make a name for himself. He had four multi-homer games in 2010 and drove in five runs on two occasions. The Astros converted him from a catcher to a first baseman after the 2008 season and, with a year at first under his belt, he's looking to fine-tune his skills.

"I'm just trying to improve on every aspect of my game, defensively and offensively," he said. "I just need to be the best I can at first base, and I think I'm getting more confidence. I'm trying to improve offensively as well."

Clemens had fewer extra-base hits and a lower on-base percentage this year. It was a challenge for him, facing tougher pitching and playing in his home state.

"It had its ups and downs, but I learned a lot," he said. "I'm not making the same mistakes, I think I learned a lot this year and feel I became a better hitter. But I'm improving and learning from my mistakes, and I'll take that to next season."

As for the Fall League, Clemens said it's been fun to play both with guys from other organizations and those already in the Houston system.

"We've got a good group of guys on this team, six or seven are Astros guys I'm good friends with, but we've definitely made some good friends here," he said. "We're all rooting in the dugout, so it's a lot of fun playing baseball that way."

NOTES: Linares, batting .393, has homers in each of his last two games. The outfielder defected from Cuba and played in only 17 Minor League games this summer before the Sox sent him West. The 26-year-old has seven RBIs in seven games. ... Blue Jays lefty Marc Rzepczynski, who spent the majority of the 2010 season in Toronto, started and held the Solar Sox to a run on six hits and three walks over six frames. He threw 78 pitches in his third start and lowered his ERA to 1.29. ... Justin Wilson (Pirates) started for Mesa and allowed one run on three hits over three frames. He struck out three and did not walk a batter.