Senators from both side of the aisle celebrated Brittney Griner's freedom from Russian detention Thursday, but several members also questioned the decision to swap Griner for known international arms dealer Viktor Bout.

Sen. Chris Coons, D-Del., told ABC News that while he sees Griner's return as "good news" and a "significant accomplishment by the Biden administration," he's worried about the precedent that could be set for exchanges of high-profile Russian criminals like Bout.

"It was clear over many months that Putin was only going to release Brittney Griner in exchange for this person," Coons said. "And that's the risk, is that the more we engage in such exchanges, the more Americans are at risk of being scooped up and held as leverage to try and secure the release of folks who we would rather not have to release."

Republicans shared Coons' concern.

"I worry about -- this sets in motion, you know, just 'grab an American,'" Sen. Lindsey Graham, R-S.C., said.

"Well, I hate it," Sen. John Cornyn, R-Texas, said when asked about the administration's move to free Bout. "But I think you're left with the decision: yes or no. And like I said, I think I would never be happy to have an American in a Russian penal colony, or under any circumstances, so unfortunately, that's the sort of way Putin does business."

Sen. Roger Marshall, R-Kan., agreed with that assessment.

"We traded a basketball player for a known terrorist criminal," Marshall said, suggesting that the U.S. should have driven a tougher bargain.

-ABC News' Allie Pecorin

Paul Whelan called CNN from prison on Thursday, saying he's "happy that Brittney is going home today and that Trevor [Reed] went home when he did -- but I don't understand why I’m still sitting here."

Whelan said he's "greatly disappointed that more has not been done to secure my release," adding, "I was arrested for a crime that never occurred."

Whelan, who has been imprisoned in Russia for nearly four years, said his message to Biden is: "This is a precarious situation that needs to be resolved quickly, and I would hope that he and his administration would do everything they could to get me home. regardless of the price they may have to pay at this point."

Biden said Thursday that the prisoner swap was "not a choice" between Brittney Griner and Whelan.

"Russia is treating Paul's case differently than Brittney's, and while we have not yet succeeded in securing Paul's release we are not giving up. We will never give up," he said.

"We'll continue to engage the Russians on Paul, and we'll continue to look at everything possible to bring him home," Secretary of State Antony Blinken added.

-ABC News' Ben Gittleson

The Phoenix Mercury, Brittney Griner's WNBA team, celebrated their star player's return Thursday.

"Miraculously, mercifully, the count of days detained has ended at 294, and our friend, our sister is headed back home where she belongs," the team wrote on Twitter. "The emotions for our organization, just like for our fans and so many across the world, are those of joyous celebration, deep gratitude, grief for the time lost, and sincere hope for all families still awaiting the return of a loved one."

Griner has played her entire nine-year career with Phoenix, making eight All-Star teams and winning the WNBA title in 2014.

The team had posted each week, saying how many days Griner had been in detention in Russia and continuing to advocate for her release. Teammates like Kia Nurse, Brianna Turner, Sophie Cunningham and Shey Peddy tweeted their relief at Griner's release.

"BG's strength in this process, her unwavering belief that resolution would come, and the hope she displayed every day is what kept all of us believing this day would come," the Mercury said in its joint statement with the Phoenix Suns.

"We no longer have to Bring BG Home -- she's on her way," they concluded.

Brittney Griner is en route to Brooke Army Medical Center in San Antonio, a spokesperson at the base confirmed to ABC News. She's expected to arrive late Thursday night or early Friday, according to the base.

-ABC News' Gina Sunseri and Ben Gittleson