SAN DIEGO -- Padres pitcher Chan Ho Park is scheduled to undergo a blood transfusion today after intestinal bleeding last week caused him to lose half of his blood volume.

Despite a battery of tests on Park over the weekend, Padres trainer Todd Hutcheson said the team still doesn't know what caused the bleeding, which stopped on its own.

"It's not uncommon for something like that to happen," Hutcheson said Wednesday. "The prognosis is really good. We have to get his red blood cells up. He's going to feel a ton better by Friday."

Besides the transfusion, Park will also be administered iron intravenously.

The Padres originally thought Park had a stomach virus, but they sent him home from Colorado on Friday when he continued to complain of abdominal pain and lethargy. Tests on Friday and Saturday eliminated a bleeding ulcer as the diagnosis.

Park went on the 15-day disabled list Sunday, retroactive to July 26, and rookie Mike Thompson started in his place that afternoon against the Rockies. Hutcheson said Park should be ready to be activated from the DL when eligible on Aug. 10.

"The only question is how much endurance he's going to have," Hutcheson said. "We think the transfusion will help with that."

Park, a 33-year-old right-hander, is 7-6 with a 4.63 ERA in 126 1/3 innings, a total that ranks second on the team behind Jake Peavy.

Barfield top rookie

Padres second baseman Josh Barfield was honored as the National League Rookie of the Month for a July in which he posted numbers rivaling the best hitters in the game.

Barfield led NL rookies with a .400 batting average and 40 hits while adding 16 runs, eight doubles, three home runs, 13 RBIs and seven stolen bases. He had a .435 on-base percentage.

Barfield's 40 hits broke the Padres rookie record of 38 by Bill Almon in July 1977 and were the fourth most in the major leagues, behind Philadelphia's Chase Utley (45), the New York Yankees' Derek Jeter (42) and Minnesota's Justin Morneau (41).

Barfield credited his work with hitting coach Merv Rettenmund, who succeeded the fired Dave Magadan in June.

"Merv has helped me with a lot of things -- having good balance, follow-through, keeping my head still, confidence, approach," Barfield said. "He's been a great fit for me."

Short hops

The Padres and Astros will wear retro uniforms from the 1976 season during the series finale this afternoon. Before the game, the Padres will honor Randy Jones, the left-hander who won the NL Cy Young Award that year by going 22-14 with a 2.74 ERA and 25 complete games. … Triple-A INF Paul McAnulty, whom Padres general manager Kevin Towers has mentioned as a candidate to be the team's third baseman next season, homered and drove in three runs Wednesday night. McAnulty is batting .320.