HOUSTON — After further thought and discussion after Sunday's game, Rays officials decided they did need to add an arm to their bullpen after all.That forced them to change their plans for slugging INF prospect Richie Shaffer , who got word mid flight to Houston that he was being sent back to Triple-A Durham.LHP Enny Romero was called up to bolster a bullpen that was down to five available relievers Monday. RHP Alex Colome needs a day or two off after throwing 50 pitches in three innings of Sunday's 5-3 loss to the Rangers.Shaffer impressed the Rays in limited opportunities during his two weeks, hitting .263 (5-for-19) with two homers. He likely would have been in the lineup Monday and Wednesday with the Astros starting left-handers."I thought 'Shaff' did a really good job," manager Kevin Cash said. "He gave some really quality at-bats for a young player; you don't always anticipate that. He showed the ability to lay off some tough pitches and connect on some tough pitches. There's a lot of talent there, and a lot of power. And hopefully we'll see him soon."Shaffer impressed the Rays further by taking a flight straight to Louisville to meet the Bulls and asking to be in the lineup, where he was at DH. Players are allowed up to 72 hours to report."We want all of our players, especially the younger ones, to value the importance of getting back down there and getting their at-bats," Cash said. "I know what the rules are, but we appreciate the guys that get down there." JUST DESSERT: Romero was eating dinner at a Brazilian steakhouse in Louisville with teammates RHP Jhan Marinez and LHP Robert Zarate when he got the call-up call, so he figured the least he could do was pick up the check. "I paid for everybody."This is Romero's fourth stint with the Rays this season; he allowed 16 hits and seven walks over 101/3 innings in his first five appearances. His work at Durham has been better, 1-1 with a 4.86 ERA in 17 games. The Rays seem to be molding him as a long reliever, as he has worked two-plus innings in nine of his past 12 appearances for the Bulls.Depending on bullpen usage, Romero's stay could be short, with RHPs Matt Andriese and Andrew Bellatti potential call-up candidates. NAVA A GO: Without Shaffer, the Rays decided to give Daniel Nava the start at first base. Though primarily an outfielder, Nava played first in 2003 at the College of San Mateo (when Henry Wrigley , a former Rays minor-leaguer, got hurt) then started again in spring training 2013 with the Red Sox. He had made 19 starts there, five this season. He played seven relatively uneventful innings at first Monday.The other reason Nava was in the lineup was to add a right-handed bat against Astros LHP Scott Kazmir .After switch-hitting most of his career, Nava tried going exclusively left-handed this season with Boston, having hit .159 right-handed in 2014 compared to .293 left-handed. But after spraining his thumb in a left-on-left at-bat, he decided to go back to switch-hitting during his July rehab assignment."(Going only lefty) was something we wanted to try — or I should say, when I was with the Sox we wanted to try," said Nava, picked up on waivers from Boston this month. "So we tried it, and it didn't turn out to be something that was good for me long term. … It just didn't work out very well." TIME OFF: Cash gave 2B Logan Forsythe a DH day to get him off his feet and said he plans to do the same with SS Asdrubal Cabrera and 3B Evan Longoria during the road trip. … LF Desmond Jennings is likely to be off tonight after playing four straight games since his return from the DL. MISCELLANY: LHP Drew Smyly felt good the day after his first start following three months rehabbing a shoulder injury. … The 14 runs allowed by Rays starters against Texas were their most in a three-game series since May 2014 vs. Toronto. … The Shaffer-Romero shuffle gave the Rays 125 roster moves since opening day. … LHP Xavier Cedeno tied a team mark by making 14 straight appearances without allowing a run or a walk; LHP Jake McGee (2013) and RHP Dan Wheeler (2009) also did so.