1. Danny Green

Danny Green has been one of the best perimeter defenders in the league of the past half decade. At 32-years-old, Green has taken a small step back over the past couple seasons. However, at 6'6" with a 6'10" wingspan, Green is still a really good defender who played a key role in two of the last six NBA champions (Spurs in 2014, Raptors in 2019). Green is also an excellent shooter (career 40.4% from three-point range) and could slot right into Houston's starting unit if the Rockets elect to move Eric Gordon back to the bench.

Normally, a player like Green would be demanding around $10-12 million in this market and out of Houston's price range, but the Rockets remain hopeful that they can land him. according to Jonathan Feigen of the Houston Chronicle. It will be tough to pry Green from the defending champion Toronto Raptors and take an undermarket deal, but undermarket deals are what Houston's known for.

2. JaMychal Green

JaMychal Green is someone the Rockets targeted at the trade deadline along with the next player on this list, Garrett Temple. The Grizzlies prioritized finding deals for Marc Gasol and Mike Conley and the Rockets had to move fast, so they opted to trade for Iman Shumpert instead. Green is a huge wing, 6'9" with a 7'3" wingspan - perfectly capable of playing and defending multiple positions. Though Green has been a slightly above average shooter for his career (36.9% from three-point range), he's shot nearly 40% from three-point range over the past three seasons.

The Clippers acquired Green with his bird-rights last season, making it really hard for a team like Houston to acquire him for the taxpayer mid-level exception. However, there's a chance the Rockets can offer a bigger role for Green than Los Angeles can. Houston's starting position may be tempting enough to sway Green.

3. Garrett Temple

Temple is another guy the Rockets targeted at the deadline, but were unsuccessful rebuffed by the Grizzlies. Temple is 6'6" with a giant wingspan of his own and he's used it successfully throughout his NBA career to be an effective perimeter defender. Temple is an average shooter (35.3% from 3-PT range), but it's his defensive versatility as a big guard who can defend forwards that would make him a preferred target for Houston.

4. Kentavious Caldwell-Pope

The Rockets have had interest in Caldwell-Pope for some time now and tried to acquire him via trade earlier this year. Caldwell-Pope has caught a bad reputation because of his contract size and his agency (Klutch Sports), but he's a legitimately capable defender for a team that's been looking for someone who can defend quick guards for the past couple years. It's one of the reasons the Rockets drafted De'Anthony Melton last summer.

5. DeMarre Carroll

Carroll was briefly a Houston Rocket in 2011, but has come into his own as a player over the past decade as a solid perimeter defender who can capably shoot open three-pointers. Carroll has been thought of as a bad contract over the past couple years due to the four-year, $60 million deal he signed with the Raptors in 2015. However, at the taxpayer mid-level exception, you could do much worse than Carroll.

*Honorable mentions: Al-Farouq Aminu, Kevon Looney, Wesley Matthews, J.J. Reddick, and DeAndre Jordan.

*Nof listed because most of these free agents will be out of Houston's price range.

It's not the end of the world if the Rockets strike out on Butler, as there are a number of quality free agents on the market and many that didn't make this list. Houston could still come out of the summer of 2019 as a significantly better basketball team by just using the tools they have on-hand. It will be interesting to see who they come out of the fray with.