The Boston Celtics is one of the most legendary franchises in the NBA. With 17 rings to their name, the team is one of the most iconic as well. Being such a prominent team, they've seen their fair share of free agent acquisitions in their day. Boston did most of their roster improvement via the draft and/or trades, but they've gotten their hands on some talented free agents as well.

Some of these signings were good. Others were downright terrible, and set the team back multiple years. Today, let's take a look at which Celtics free agent signings are the best of all-time.

Keep in mind that the Celtics have historically not had a lot of success attracting free agents to Boston. Many of their legends and stars are either home-grown (Paul Pierce, Larry Bird, and today, Jayson Tatum and Jaylen Brown), or were acquired via trade (Ray Allen, Kevin Garnett). Still, there's been a handful of players that came over via trade that helped Boston greatly.

8. Shaquille O'Neal

Well, ranking a Top 75 All-Time player here feels low, huh.

Most fans know by now that towards the tail end of his career, Shaquille O'Neal bounced around different teams. One of the teams he signed with was with the Celtics, back when he was a free agent in 2010. At the time, Shaq was already 38 years old, hobbled by multiple injuries he accrued over the years. He was still a big body for Boston, but that was basically it.

O'Neal's stint with the Celtics was largely unremarkable. He averaged 9.2 points and nearly five rebounds per game, but injuries limited him to just 37 games in the regular season. Boston made it to the playoffs, but they fell to one of Shaq's old teams in the Heat in the Eastern Conference Finals. O'Neal was largely ineffective during this playoff run.

After this season, it was clear that Shaq didn't have anything left in the tank. He proceeded to retire after the season, ending his career on a rather unsatisfactory note.

7. Xavier McDaniel

Xavier McDaniel was signed by the Celtics back in the 1992 offseason. At the time, the franchise was still reeling from the retirement of Larry Bird. The team desperately needed to have a jolt at the forward position. With that in mind, they poached the discontented McDaniel from their rival Knicks.

The Celtics were hoping to get something close to what McDaniel was in Seattle. As a member of the SuperSonics, the forward was a 20-PPG scorer who placed second in ROY and was an All-Star at one point. However, McDaniel simply couldn't muster up the same performance for the Celtics during his three seasons there. He averaged just over 11 points per game in Boston, and the Celtics were unable to advance past the first round. He was eventually let go, and he proceeded to play in Greece.

6. Evan Turner

One of the few marquee signings for the Celtics in recent memory, Evan Turner was signed by the Celtics in 2014 after the end of the Big 3 era in Boston. With players like Allen, Garnett, and Pierce leaving, the Cs wanted someone who could step in and help pilot the offense.

Like most of their signings, though, the Celtics got Turner a little too late in his career. Turner was not able to capture the same form he had during his time with the Sixers, averaging nearly 10 points per game. He was an effective playmaker, though, dishing out five assists per game during his time. Unfortunately, Turner's deficiencies on offense (lack of a consistent three-ball) hindered his ability to be successful in Boston. He would proceed to sign in 2016 with the Blazers are part of the infamous cap spike.

5. Dominique Wilkins

Similar to Shaq's case, ranking a Top 75 All-timer this low feels weird. However, ‘Nique had a much better go-around in Beantown than Diesel.

Casual fans might not even know that ‘Nique suited up in green during his career! Before signing with the Celtics as a free agent, Wilkins was most known as the focal point of the Atlanta Hawks. His high-flying act and electric showing was the main event in Georgia basketball for quite some time. During the 1994 season, though, ‘Nique decided to take his talents to Boston.

At the time, Wilkins was the biggest free agent signing in Celtics history. However, Wilkins didn't exactly live up to the hype he generated. At 35 years old, people started to see the signs of a slow decline. It became much more prominent in Boston: ‘Nique averaged 17.8 points per game, well below his 26.4 average in Atlanta. His three-point shooting improved, but most of his other stats saw a sharp decline. Boston managed to squeeze into the playoffs with a 35-47 record, but they were immediately bounced by Shaquille O'Neal's Magic in the first round.

Since we're taking into account the player's time with the team, Nique unfortunately ranks this low.

4. James Posey

James Posey is so much more different than all the other names on this list. While other players here were either star players or former stars, Posey was most knows as a role player. Additionally, Posey only stayed with the Celtics one year, signing with the Hornets after the 2008 season.

So why is Posey ranked this high in the list? Well, its simply because Posey was a critical part of Boston's championship team in 2008. The Celtics brought him in as a free agent specifically as a defensive stopper. Posey guarded the likes of LeBron James and Chauncey Billups en route to the Finals, and he took on the challenge of guarding Kobe Bryant in the finals. His work in defending Kobe warrants attention on this list. The timely baskets in the playoffs certainly don't hurt his case, either.

While Posey's production was less than other players on this list, he was critical to a championship in Boston: something that none of these players can say for themselves.

2. Kemba Walker

Now, we get to the most recent acquisitions, which also happen to be the best as well. First up, we have Kemba Walker signing with the Celtics as a free agent in 2019. Walker's arrival came right after Kyrie Irving and Al Horford's departure, which was perfect for Boston. After a terrible playoff performance, the team badly needed a point guard who could approximate Walker's skills.

Walker's first year in Boston came during the COVID-19 pandemic. During that period, the Celtics went all the way to the Conference Finals in the Bubble, with Kemba being a key part in their success. The following season, though, was, much, much worse. Walker struggled with injuries all season long, and Boston was bounced by the eventual champions Bucks in the first round. Shortly after that, Walker was traded to the Thunder for, ironically, Al Horford (more on him later).

2. Gordon Hayward

Oh, Gordon Hayward. What could've been? Hayward was signed by the Celtics in 2017 as part of their all-in push for a title. Hayward joined a star-studded roster that boasted the likes of Kyrie Irving, Al Horford, and a young Jayson Tatum and Jaylen Brown.

Hayward's very first game with the Celtics immediately went awry. By now, you probably know what happened to Hayward in his first game. While going up for an alley-oop attempt, the forward landed awkwardly and violently fractured his leg. He would miss the entirety of the 2017-18 season, and would return the following season.

To be fair, Hayward posted respectable numbers once he returned to the court. He even had a 17.5 PPG season during the 2019-20 season, which was when they made it all the way to the Conference Finals. However, he just wasn't the same player that the Celtics were hoping for. That's not entirely his fault, it's just a tragic tale all-around.

1. Al Horford

Is it weird to say that Al Horford is the Celtics' best free agent signing? From a casual standpoint, one could see that. However, when you take a deeper look into Horford's tenure with the Celtics, it's easy to see that that's the case.

Horford signed a deal with the Celtics during the infamous 2016 offseason. While most of the deals at the time aged poorly, Horford's contract didn't. He wasn't a flashy center that scored in bunches or blocked shots with aplomb, but that was never Al's game. Instead, Horford focused on his game on solid defensive fundamentals, a solid three-point stroke, and playmaking from the post. He was a key part in Boston's game plans against the talented big men that would eventually dominate the Eastern Conference.

While his second stint doesn't count towards this ranking, it's still worth a mention. After returning to Boston via the Walker trade, Horford continued to prove why he's arguably the best big man Boston has had since Kevin Garnett. His size continued to torment Joel Embiid and Giannis Antetokounmpo. His big games fueled the Celtics during their run to the Finals. Make no mistake about it: Al Horford is incredibly important to the Celtics, and his arrival in Boston is one of the reasons why they've been a baby dynasty in the last decade or so.