A visit to the tropics might be just what Lucas Duda’s barking lower back needs. The tropics can be equated to New York, which is where the Mets were headed Thursday night after departing frigid Coors Field. Manager Terry Collins wasn’t going to take any chances with Duda’s back given the fact it was 28 degrees. Duda remained on the bench in the Mets’ 11-3 loss to the Rockies. Duda incurred stiffness in the back while taking a swing in the second game of a doubleheader against the Rockies on Tuesday. Jordany Valdespin (2-for-4, run scored) moved to left field in Duda’s place. “The pain wasn’t too bad, but there is a process we want to make sure he goes through before he’s ready,” Collins said before the Mets’ 11-3 loss to the Rockies. “And [28] degrees is not really the time to test it.” * Collins downplayed a comment he made on WFAN on Wednesday, when he said the Mets might need to consider promoting top pitching prospect Zack Wheeler “pretty soon” given the state of the rotation. “We don’t know,” Collins said. “That’s why you have to be careful what you say, because ‘soon’ can mean July. To you guys, it’s Friday, so there’s a big difference. We’re sitting here thinking the All-Star break might be soon, so it’s a little different dynamic.” * The Rockies announced that Wednesday’s snowed out game against the Mets has been rescheduled for June 27 at 6:10 p.m. The Mets are scheduled to finish a two-game series against the White Sox in Chicago a night earlier. * Shaun Marcum, who is recovering from neck stiffness, threw 41 pitches in an extended spring training game yesterday in Port St. Lucie. The right-hander did not allow a hit or walk and struck out five. Collins indicated Marcum will need at least another appearance in Port St. Lucie, perhaps throwing 85-90 pitches, before he is considered for the Mets’ rotation.