The Mets’ hopes of making a splash acquisition before Opening Day ended last night, when Michael Bourn agreed to a four-year contract worth $48 million — with a fifth-year vesting option — with the Indians, a major league source confirmed. In the end, it was the Mets’ refusal to surrender the No. 11 overall selection in the June draft and their refusal to include the option year that doomed their chances of getting Bourn. An industry source involved in the negotiations said Bourn was contemplating a four-year offer worth about $48 million from the Mets — contract negotiations were down to “small details” such as a hotel suite on the road for the player — but Bourn wasn’t about to wait 2-3 weeks for a ruling on the Mets getting their top draft pick protected. The Mets believe Bourn would have accepted their offer if the draft-pick issue could have been resolved in the next few days. However, a source said he preferred the Indians because they’re closer to contending. Though only the top 10 picks in the draft are protected, the Mets had argued to MLB that their No. 11 pick deserved such status because the Pirates only moved ahead of them to No. 10 as compensation for failing to sign their top pick last year. The Mets contend that wasn’t in the spirit of the rule. The Mets believed the issue could be resolved by an arbitrator in a matter of days if needed. But when team officials contacted the commissioner’s office yesterday they were informed the process would take 2-3 weeks. Bourn, the source said, wouldn’t wait that long and accepted the Indians’ offer, which contains a fifth-year vesting option worth $12 million. “A couple of days he would have waited,” the source said. “Not a couple of weeks.” Bourn, 30, would have given the Mets a legitimate leadoff hitter and center fielder. The team will go with a likely combination of Kirk Nieuwenhuis and Collin Cowgill playing center field with Ruben Tejada probably headed for the leadoff spot.