In 1961 at age 19, he was signed by the Boston Red Sox as an amateur free agent. Petrocelli played three seasons in the Red Sox minors, getting a one game call up in 1963. He was brought up for good in 1965 and became the Red Sox everyday shortstop for the next decade.
Rico batted .232 with 15 doubles & 33 RBIs making the Topps All Star Rookie team. He hit for some power, which was still rare in the sixties. He hit 13 HRs that season followed by 18 in his sophomore year.
In the Red Sox 1967 "Impossible Dream" AL pennant winning season, he hit .259 with 17 HRs 24 doubles & 66 RBIs,. He began the year with a three run Opening Day HR & finished up April batting .333. By the All Star break he had 9 HRs with 38 RBIs, getting to start at third base while batting 8th for the American League in the All Star Game in Anaheim.
In the September pennant race he began the month driving in runs in five straight games, including hitting a HR off New York's Mel Stottlemyre, then driving in Hawk Harrelson to lead the Sox to a 3-1 win on September 7th. On September 13th he drove in three runs, with a double leading Boston to a 4-1 win. On September 20th, Petrocelli hit a 6th inning HR off Cleveland's Sudden Sam McDowell putting the Red Sox ahead for good in the 5-4 win.
Post Season: He was batting just .071 after the first five Series games, against the St. Louis Cardinals, then had a big Game #6. He hit two solo HRs off Dick Hughes (Carl Yastremski & Reggie Smith also homered). The Red Sox backs were against the wall, but the 8-4 win forced a Game seven. He doubled & struck out twice in the Game #7 loss to Bob Gibson.
Over the next two seasons he led all AL shortstops in fielding percentage, turning 102 double plays (second in the AL) in 1969. Also in 1969 he set a single season record for most HRs by a shortstop with 40 (4th in most the AL).
He also had career highs in doubles (32) batting average (.297) & on base % (.403) as the Sox finished in third place. His 97 RBIs were ninth in the league, followed by a career high 103 RBIs in 1970 (sixth most in the AL) as well as 29 HRs (8th in the AL).
Petrocelli played at shortstop until 1971, then moved over to third base, when the Sox acquired Hall of Famer; Luis Aparicio. At third, Petrocelli once again led the league in fielding percentage (.976) making only 11 errors in 463 total chances. In 1972 he posted a .970% which was second best in the league. After his 1972 season when he hit 28 HRs with 89 RBIs, his numbers tailed off as injuries began to plague him.
In 1973 he played in a career low up to that point 100 games with 129 in 1974. In 1975 he enjoyed his last full time season, winning another pennant with the Red Sox in their 95 win season under Darrell Johnson. Petrocelli played 115 games, with former Met Bobby Heise playing behind him. Rico hit 7 HRs with 15 doubles 59 RBIs & a .239 average.
In a May preview of the ALCS, Petrocelli hit two HRs & drove in four runs hitting safely in all three games at the Fenway series sweep. In June he had a five game & six game hit streak driving in 16 runs in the month. He missed over two weeks of action in August, then had a quality return in September. He hit safely in 12 of the last 15 games, with 3 HRs & 15 RBIs in the month.
Post Season: In Game #2 of the ALCS he hit a HR off Oakland’s Rollie but only hit .167 overall in the series. In the classic 1975 World Series against the Cincinnati Reds, he opened up Game #1 with two hits a double, a walk & a pair of RBIs in the Red Sox win. In that game Luis Tiant shut out the Reds & Don Gullet on a five hitter.
Petrocelli had two hits in each of the first three games, hitting safely in the first four. He drove in the second run of the game off Gullett in the Sox three run 3rd inning. Overall he hit .308 (8-26) with three walks, driving in four runs against the Big Red Machine.
He played in 85 games & then retired after the 1976 season, as Butch Hobson took over third base. In his 13 year career, Petrocelli hit .251 with 1352 hits, 210 HRs 237 doubles 22 triples 653 runs scored 773 RBI and a .332 on base% in 1553 games.
He posted a .969 fielding percentage at short stop (93rd all time) & a .970 fielding% at third base (5th best all time). He was inducted to the Boston Red Sox Hall of Fame in 1997.
Retirement: After his playing days, Petrocelli was a Red Sox radio broadcaster in 1979. He also hosted a TV game show for Candlepin Bowling (1980-1983). He was also a manager for the Red Sox minor league AAA ball Pawtucket team, in 1992.
He now runs Petrocelli Sports which handles speaking engagements & sports memorabilia functions.
He also heads the Petrocelli Marketing Group that sells customizes shirts & promotional products. Earlier in the sixties he opened up a small chain of gas stations with other Red Sox players.