Cardinals manager Mike Matheny said Carlos Martinez will go to the bullpen.
''We are just in a spot where we've got to try and figure out what is best for our club,'' said Matheny, noting that Martinez is a proven commodity in the bullpen.
Kelly lost a competition last spring to Shelby Miller, but moved from the bullpen to the starting rotation later in the year. He started 15 games for the Cardinals in the regular season and four more in the postseason and has a 3.08 ERA.
Martinez thrived in the setup role late last season, including in the playoffs. He will return to eighth inning duty, setting up closer Trevor Rosenthal, despite allowing only three earned runs and striking out nine in 15 1-3 spring innings.
''I believe that he is eventually going to be a starter and I believe he is going to be a very good one, but right now we need him to help our club out of the bullpen,'' Matheny said.
Kelly's control fluctuated in Sunday's start, during which he struck out five but also walked four. He allowed two runs and two hits in the sixth and didn't get an out before being lifted.
''I wouldn't say it was great, by any means,'' Kelly said before learning he would be in the rotation. ''The walks are just something that I absolutely don't like.''
Shortstop Jhonny Peralta gave the Cardinals the lead in the second with his third homer of the spring. Matt Holliday hit his first in the third and Matt Adams also connected in the third, a two-run shot off Astros starter Jerome Williams.
Williams gave up six runs and nine hits in four innings.
''It was one of those days where balls were finding the bats and balls were finding the holes,'' Williams said. ''I left about three or four pitches up and they took advantage of them.''
Closer Trevor Rosenthal took a comebacker off his backside in the ninth. The ball caromed to third baseman Daniel Descalso, who threw to first in time to get Marwin Gonzalez. Rosenthal remained in the game and recorded the save.
Astros: Williams has allowed 10 runs in 7 2-3 innings over his past two Grapefruit League outings.
''It's kind of bad that it's happening now at end the of spring,'' Williams said. ''Hopefully I can just turn it around before the season starts.''
Cardinals: While Matheny named Kelly to the starting rotation, he declined to give the order in which the starters will appear. Adam Wainwright will be the Cardinals opening-day starter. He will be followed, in an order to be announced later by Lance Lynn, Michael Wacha, Shelby Miller and Kelly.
Cardinals: Jaime Garcia threw a 25-pitch bullpen session from the mound for the first time since the second week of spring. Garcia had experienced soreness in his surgically-repaired shoulder. He was expected to contend for the Cardinals' fifth starting spot before experiencing the discomfort.
Reliever Jason Motte is scheduled to long toss on Monday as he works his way back from ligament replacement surgery.
The competition to become Houston's closer will likely extend beyond spring training.
''I think that we will go into the season with a closer-by-committee and try to look at the best situation given that night, given that game,'' manager Bo Porter said.
None of the five pitchers in contention for the job have pulled away from the pack this spring. The group includes Chad Qualls, Josh Fields, Kevin Chapman, Matt Albers and Anthony Bass.
Qualls appeared to be the favorite entering Grapefruit League games.
''I think all of those guys have done a really good job,'' Porter said. ''When you don't have one guy that has separated himself, you would rather it be the way it is where all those guys are throwing the ball well, which is a good problem to have.''
Should the competition continue into May, Jesse Crain could also become a contender. The Astros signed Crain as a free agent over the winter, but he is still rehabbing from offseason biceps surgery.
The Cardinals sent five players to the minors - one of whom was 23-year-old Aledmys Diaz. The newly-signed Cuban shortstop went 3 for 5 in two major league games before heading to Double-A Springfield.
''He just kind of plays a little more experienced baseball than you would expect him to,'' Matheny said.
DOWN TO THREE
St. Louis also optioned reliever Sam Freeman and outfielder Joey Butler to Triple-A Memphis. With Freeman gone, that leaves Jorge Rondon, Keith Butler and Scott McGregor competing for the final spot in the Cardinals' bullpen. The Cardinals also optioned infielder Greg Garcia to Triple-A Memphis and re-assigned infielder Luis Mateo to minor league camp.
MORE TO COME
Porter expects first baseman Chris Carter to produce better offensive statistics than 2013's breakthrough season in which he hit 29 home runs but only posted a .223 average.
''I think just the experience of playing every day last year will help in that regard - lower strikeouts, more contact, more homers,'' Porter said.