The incoming Minor League players getting the most attention in the Astros' system these days are the more than a dozen youngsters the team has acquired via trade in the month of July, giving Houston more prospects to bolster its future.

There is another group of newcomers, however, making waves down on the farm.

Several of the Astros' top picks from this year's First-Year Player Draft are off to quick starts. The majority of the draftees are at short-season Tri-City, which is where the Astros typically send players drafted out of four-year colleges.

Leading the way at Tri-City is the starting pitching staff. The top four starters for the first-place ValleyCats entered Sunday a combined 17-3 with a 2.03 ERA -- right-handers Aaron West (5-0, 0.97 ERA), Brady Rodgers (4-1, 1.62 ERA), Vincent Velasquez (4-1, 2.97 ERA) and left-hander Brian Holmes (4-1, 2.55 ERA).

"The entire Tri-City pitching staff has pitched very well," Astros director of player development Fred Nelson said.

Rodgers was drafted in the third round, West in the 17th round and Holmes in the 13th round. Holmes had a perfect game through six innings of a seven-inning game Friday. Velasquez was drafted in the second round in 2010, but missed all of last season following Tommy John surgery.

"We're monitoring the innings he's going to pitch," Nelson said. "West, the kid from the University of Washington, is off to a good start."

Offensively, fifth-round pick Andrew Aplin, an outfielder, is hitting .357 with three homers and 17 RBIs through 35 games; seventh-round pick Preston Tucker, an outfielder, is hitting .300 through eight games; infielder Austin Elkins, a 19th-round pick, is hitting .346 with three homers and 18 RBIs through 35 games; and catcher Tyler Heineman, an eight-round pick, is hitting .319 with 13 RBIs.

"They've all played real well for the first time out," Nelson said. "It's a good club and they've played like it."

Tri-City won its fourth consecutive game Sunday night to improve to 30-11 on the season, including 18-3 on the road. Joe Bircher started and went five innings and allowed five hits and three runs (one earned). He was drafted in the 10th round this year.

Nelson watches Draft picks in Florida

Astros director of player development Fred Nelson recently returned from Florida, where he got a chance to see three of the club's top Draft picks from this year -- No. 1 overall pick Carlos Correa, No. 41 overall pick Lance McCullers Jr., and fourth-round pick Rio Ruiz.

Correa, a shortstop from Puerto Rico, got off to a slow start in the Gulf Coast League, but he's starting to come around as he gets adjusted to a new way of life. He was hitting .221 with two homers and five RBIs through 28 games. Ruiz, a third baseman the Astros believe was a first-round talent, was hitting .306 with seven RBIs through 13 games.

"[Ruiz] had been DHing when he came to us, and he was a little bit out of shape because of some of the medical issues he had," Nelson said. "He's worked very hard and is a likeable young man. I saw him play two games at third base and he swung the bat really good. Both those two players are going to be good players in the future."

Meanwhile, McCullers was 0-1 with a 2.25 ERA in three starts. He has thrown a total of only eight innings as the Astros keep him to a strict limit of three innings or 45-50 pitches per outing. Nelson said McCullers would make one more start in the Gulf Coast League before being moved to rookie league Greeneville.

"That will give him a chance to pitch at night," he said. "We slated it out, and if he does that, it would be three or four starts. If that club makes the playoffs, he will have a chance to get in there and get another start or two. That would be a pretty good summer for him."

Houston tries to figure out blister problems

The Astros are going to try to send top pitching prospect Jarred Cosart to a specialist of some sort to see if they can find a remedy for his recurring blister problems.

Cosart, who had his return start to Triple-A Oklahoma City cut short after 3 2/3 innings because of another blister, appeared to have gotten over his problems. Cosart went 5-5 with a 3.52 ERA in 15 starts at Double-A Corpus Christi and has now dealt with three blisters on three different fingers.

"We've had all kinds of gook and gunk and some rodeo cream -- a bunch of stuff," Astros director of player development Fred Nelson said of attempted remedies.

Nelson said the Astros have had a rash of blister problems with pitchers this year and have examined everything from weather conditions to the baseballs themselves to try to determine a cause.

"We've had more in this organization than I have ever seen," he said. "We've talked about the balls, being out in California [Lancaster] where it's gritty and grimy and in the desert environment. It's frustrating for [Cosart]. He'll get through it and press forward."

Mier might not return to Class A in near future

The chances of former first-round pick Jiovanni Mier returning to Class A Lancaster in the near future appear to be diminishing.

Mier, the Astros' top pick in the 2009 Draft, hasn't played since May 4 because of a pulled hamstring. Mier has been rehabbing with the Astros' Gulf Coast League team in Kissimmee, Fla., and will likely resume his season there when he's healthy. Mier was hitting .309 with two homers and 13 RBIs in 26 games.

"He's not quite ready yet and he's very frustrated," Astros director of player development Fred Nelson said. "He just can't seem to get over the hump. He's close, but he's been away so long we're going to be forced to keep him down there. He can play some Gulf Coast League games on rehab and it would give him a chance to take some ground balls and see some pitches before we throw him back out in the fire."

A year ago, the Astros hired a rehab coordinator who's stationed in Kissimmee and is there to work with players who are going to be on the disabled list for extended time or with players who have specific types of injuries.

Worth Noting

The Astros' top four Minor League clubs were 235-187 entering play Sunday. They were a combined 202-329 overall last year.

After going 3-1 with a 5.57 ERA in four starts in Double-A, right-hander Bobby Doran was sent back to Class A Lancaster to make room for three starters the Astros received in July trades -- Rob Rasmussen, Matthew Heidenreich and Asher Wojciechowski.

Center fielder Austin Wates has been placed on the disabled list at Double-A Corpus Christi with a strained groin and has been replaced by Robbie Grossman, who's expected to start in center the rest of the season. Grossman was acquired from the Pirates in the Wandy Rodriguez trade.