Long went to Mets Spring Training in 1999 & made the team after having a good run. He would make three appearances as a pinch hitter as a New York Met, going 0-3. He was sent to AAA Norfolk, where he batted .326 with 7 HRs 20 doubles & 47 RBIs playing in 78 games. Then in July he was traded to The Oakland A’s for veteran pitcher Kenny Rodgers. Rodgers helped the Mets win the 1999 wild card race, going 5-1 with a shutout & two complete games. But he had a bad post season, going 0-2 & walking in the winning run of Game #6 of the NLCS in Atlanta.
Terrence Long went on to make his debut in Oakland the next year, as the teams main centerfielder. He batted in the leadoff spot & sparked an Oakland team to four straight post season appearances. In 2000 he batted .288 with a career high 18 HRs & 104 runs scored. He drove in 80 runs hit 34 doubles with four triples posting a .336 on base %. Long came in second in the Rookie of the Year voting to Seattle’s Kazuhiro Sasaki. Long & the A’s got to the 2000 ALDS where he only batted .158 but he did hit one HR in Game #3 off Orlando Hernandez.
Over the next two seasons, Long would play in every game of the regular & post seasons for the Athletics. He would hit 30 or more doubles for three straight seasons & hit 14 or more HRs for four straight years. With Oakland he would get to four straight posts seasons but lose in the first round each time. In 2001 Long would bat .283 with 12 HRs 37 doubles & a career high 85 RBIs.
Post Season : That year in the ALDS he hit .389 (7-18) with a pair of HRs & three RBIs. In Game #1 he hit a fourth inning, lead off HR off Roger Clemens & in the top of the 8th hit another off Sterling Hitchcock. The A's won the game 5-3 on the road. Long would hit safely in all five games, driving inn another run in the Game #4 loss. The A's started out the series with a two games to nothing lead, but lost the final three games. His average fell off to .240 in 2002 but he did hit 16 HRs with 32 doubles & 67 RBIs.
In 2003 he hit just .245 & the A’s traded him along with catcher Ramon Hernandez to the San Diego Padres for Mark Kotsay. It was a big trade at the time, but neither player worked out for too long. In one season at San Diego, Long batted .295 in 136 games (just 288 at bats) but only hit three HRs with 28 RBIs. In the outfield he made twelve assists which was second most in the NL.
After the season he was traded to the Kansas City Royals for Darrel May & Ryan Bukvich. Longs career winded down quickly, he signed with the Cincinnati Reds in 2006 but was released. He got picked up by the A.L. New York team, playing in 12 games.
After eight seasons, Long batted .269 with 824 hits 69 HRs 166 doubles 21 triples 428 runs scored 376 RBIs & a .318 on base % in 890 games played.