Williams, who won 10 games with the Giants last season, and Aardsma were both high draft picks. Williams was chosen 39th overall in 1999 and Aardsma was taken 22nd overall in 2003, after leading Rice to a national championship.
Both will be sent to the Minors, but are clearly in the Cubs' plans, with general manager Jim Hendry optimistic that the two could make an appearance with the club later this season. Hawkins' role had diminished after blowing four of his eight save opportunities this year.
Last year, Williams, 23, became the Giants' youngest pitcher to win 10 games in a season since 1975. His father's severe illness limited his time in Spring Training this season and Williams has spent most of 2005 with San Francisco's Triple-A affiliate in Fresno.
Williams has struggled at Triple-A, going 1-4 with a 9.39 ERA in six starts. Hendry said that the lack of preparation before the season hurt him.
"Jerome had a very short Spring Training with his father's illness, and he's behind a little bit," Hendry said. "He really needs to obviously get a little better before we think about bringing him up. At 23, he's very, very talented and was well on his way in 2003 and 2004 to outstanding rotation performance."
Aardsma, 23, had a fast track to the Big Leagues, making his Major League debut 10 months after being drafted. He has spent most of his career in the bullpen for the Giants' organization, but recently the club moved him to the starting rotation in Norwich (Double-A) to give him more innings. In nine games, Aardsma has gone 6-2 with a 2.93 ERA.
"We'll let him pitch awhile and then try to decide whether we think he's better suited for the 'pen or as a rotation guy," Hendry said.
Hendry said that the club has been in talks with other teams for weeks about possible deals involving Hawkins.
"We've been getting a regular amount of calls for LaTroy lately and honestly, in the best interest of LaTroy and his career, also it's a good situation for him," Hendry said.
Hawkins has had a bit of an embattled career with the Cubs since signing with the team as a free agent prior to the 2004 season. Hawkins was signed primarily as a set-up man, but pitched mostly in the closer role last season after Joe Borowski was shelved with a shoulder strain for the rest of the year.
In 98 games with the Cubs, Hawkins had a 6-8 record with a 2.76 ERA. This season, Hawkins has struggled, blowing two save opportunities at home with a one-run lead in the ninth. Overall, Hawkins is 1-4 with a 3.32 ERA in 21 games this season.
"You can't ever pinpoint why something doesn't work," Hendry said. "Obviously, LaTroy is a very talented guy -- probably the hottest ticket set-up guy available at the time -- and we were ecstatic to get him.
"It just didn't work. I think he'll go somewhere and do well. He's still throwing hard, and sometimes a change of scenery is the best."
Some questioned the timing of the trade with Mark Prior being put on the disabled list after being struck by a line drive to his throwing elbow. Hendry said that it's purely coincidental.
"Absolutely not," Hendry said of whether the injury had an impact on the trade. "In fairness to this deal, if we could have made this deal a week or two weeks ago, we would have. To get these two guys back in return -- certainly high-profile prospects, one guy already won 10 games in the Big Leagues at age 22 -- we feel very pleased."
Kelly Thesier is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.