(D.C. United)

D.C. United addressed its unsound defense Thursday by making a big splash in the usually quiet first stage of MLS’s re-entry draft, acquiring right back Sean Franklin and center back Bobby Boswell, the league’s defender of the year with United in 2006.

Franklin, 28, was a starter for most of his six years with the Los Angeles Galaxy and won two MLS Cup titles. Boswell, 30, was the centerpiece of Houston’s backline for six seasons.

“Once we saw the list of players available — and it was a very good list — we saw a chance to grab two who we thought would really help us,” United General Manager Dave Kasper said.

Both are expected to start for United, which this past season finished with the fewest victories in league history (3-24-7) and conceded the second-most goals in the 19-team league (59).

Bound in most cases to honor a player’s contract option, teams typically pass in the opening segment of the draft and wait for the second stage a week later, when they are free to negotiate new deals with discarded players. Only six were selected in the first stage the previous three years. Five were chosen Thursday.

United did not want to wait. It claimed Franklin with the first overall pick and Boswell in the second round. Consequently, the club agreed to pay Franklin his promised salary in 2014 — an estimated $225,000 — and had to follow guidelines in the collective bargaining agreement to sign Boswell, whose contract expires this month.

Players age 30 or older with eight or more years of experience who are out of contract are guaranteed 105 percent of their previous salary. Boswell made $220,000 this year and will take home $231,000 next season.

United is flush with salary cap space after releasing several players, including top-earner Dwayne De Rosario ($370,000 of his $600,000 figure counted against the cap).

In hopes of landing both Franklin and Boswell, United had reached out to their representatives in recent days to gauge interest in coming to Washington.

“I had an idea I might end up back in D.C. I just had to wait to see if I would still be available,” said Boswell, who starred for United between 2005 and ’07. “I was a youngster last time, and now I come back with more experience. I’m happy to go back — love D.C.”

Boswell is expected to partner with Dejan Jakovic in central defense.

United never truly filled the long-term void left by Boswell when it dealt him to the Dynamo for goalkeeper Zach Wells after the 2007 season. Wells played one year for United before deciding to retire, while Boswell anchored two MLS Cup appearances.

“We let Bobby go too easily, for sure,” said Kasper, who has overseen United’s roster for 11 years. “At the time, Bobby wanted a change and we needed a goalkeeper because Troy [Perkins] wanted to go to Europe. … Bobby has taken good care of himself and is at a great age: He’s experienced and he’s a competitor.”

United had attempted several times to trade for Franklin, the 2008 MLS rookie of the year. It jumped at the opportunity to claim him without surrendering any assets. He is likely to supplant Chris Korb as the first-choice right back. Korb would provide cover on the right and remain an option on the left, where he played periodically the past three seasons.

Earlier this week, United acquired veteran midfielder Davy Arnaud, 33, from the Montreal Impact for an international roster slot in 2014 and ’15.

“We’ve had a very good week,” Kasper said, “but there’s still a lot of work to do.”

United will have the first pick in the second stage of the re-entry draft Wednesday, in the college draft Jan. 16 in Philadelphia and in the allocation order, utilized when most U.S. national team players sign with MLS.

In other roster news …

United remains in contact with at least two players it exposed in the re-entry draft: defenders Daniel Woolard and James Riley and midfielder John Thorrington. None was selected in the first stage. Clubs are permitted to re-engage with such players leading to the second stage. “It’s possible one or more will return to the team,” Kasper said.

Kasper is optimistic the club will reach a deal with English club Derby County to permanently acquire forward Conor Doyle, who joined United on loan for the last half of the 2013 season. An agreement is probably five to seven days away, Kasper said.

Defender Dennis Iapichino, acquired from Montreal late in the season, will not return. The Swiss left back wanted to explore options in Europe, Kasper said.