With Delonte West sidelined by a sprained right ankle, the Celtics were leaning on rookie Avery Bradley as the primary reserve ball handler on an overhauled second unit. With Rondo's playing time escalating, including a team-high 42 minutes in Friday's win over the Golden State Warriors, Boston decided to use a roster spot that will open with Chris Johnson's expiring 10-day contract to add Arroyo.
Celtics coach Doc Rivers says that Arroyo will join the team on Monday.
Arroyo, a ninth-year point guard, was jettisoned by the rival Miami Heat earlier this week to make room for bought-out Mike Bibby. Arroyo averaged 5.6 points and two assists per game in 49 appearances with the Heat, starting 42 games before his departure.
The 31-year-old Arroyo also has 34 games of playoff experience, including being with Miami for last year's first-round battle with the Celtics.
While the move is unlikely to tweak the Heat much, the Celtics do add a player who spent much of the season with a rival (certainly a benefit for any late-season addition). Boston also won a tug-of-war with the Heat earlier this week for the services of backup forward Troy Murphy.
Arroyo is unlikely to have much of a long-term impact if West is able to get (and stay) healthy, but Boston hasn't had a pure backup ball handler behind Rondo very often over the past two seasons and it provides yet another veteran body whom Rivers can toss out there when the situation allows. Projecting a 12-man roster for the postseason, it seems unlikely Arroyo would even make that cut should Boston get all of its players healthy (a big if for a Celtics team battered and bruised all season).
Johnson said he's not disappointed about not getting re-signed by the Celtics and that he enjoyed his time in Boston, but it's back to Dakota of the D-League for the lanky center.
"I worked hard, did whatever I could do in 10 days," said Johnson, who saw limited action after a brilliant debut in Denver for a short-handed Celtics squad that made three moves and traded away five players (including two centers) at the deadline. "Everybody saw I work hard and I felt like I left a mark."
The Celtics wouldn't mind crossing paths with Johnson down the road, particularly if he can add muscle mass to his frame. But they were brutally honest about their needs moving forward.
"They just want a guard to give Rondo some rest, especially with [Delonte West] hurt," said Johnson.
Chris Forsberg covers the Celtics for ESPNBoston.com. Information from The Associated Press was used in this report.