Eddie Butler, 27, secured the final bullpen spot and could serve a long-relief role. The right-hander, who is out of options, appeared in six spring games, making three starts, and gave up seven earned runs over 15 innings. Last season, Butler pitched in 13 games for the Cubs and made 11 starts, posting a 3.95 ERA.
The Cubs will cary eight relievers, and the only question late in spring was whether Strop was ready to go.
Jon Lester got the regular season underway on Thursday against the Marlins, heading an impressive rotation that includes Kyle Hendricks, Yu Darvish, Jose Quintana and Tyler Chatwood.
This will be the first time Victor Caratini, Ian Happ and Butler are on the Cubs' Opening Day roster. Happ, 23, was called up May 17 last season and belted 24 homers in 115 games.
Infielders Ryan Court and Mike Freeman, who were assigned to Minor League camp on Thursday, impressed manager Joe Maddon in Spring Training.
"Court showed to me he's a really good baseball player," Maddon said of the Elgin, Ill., native. "I put a lot of signs on with him, whether he was on the bases or at the plate, and he didn't miss one. That tells me a lot about his ability to be in the moment."
The Cubs also optioned right-handed pitcher Shae Simmons to Triple-A Iowa. Simmons was slowed by injury in Spring Training, and only appeared in four games.
Catcher (2): The only position battle this spring was who would backup Willson Contreras. The Cubs picked Caratini over veteran Chris Gimenez, and will see if Caratini gets enough at-bats.
First base (1): This is Anthony Rizzo's spot and the only question is who will back up him when he gets a day off. Ben Zobrist played some first base this spring and could give him a break.
Second base (2):Javier Baez and Zobrist will share second base. Baez will likely get more playing time.
Third base (1): This is Kris Bryant's fourth season, and his spot. He struck out 11 times but also drew nine walks, while batting .366 this spring. He hit one home run in the Cactus League. Not to worry. They'll come.
Shortstop (1):Addison Russell looked sharp this spring, batting .326 in 18 games.
Utility (2): Versatility is key to winning a spot on Maddon's roster. The left-handed option on the bench will be Tommy La Stella, who batted a career-high .288 last season. Zobrist may be Mr. Everything again.
Outfield (3): Happ and Albert Almora Jr. are expected to share center field, although Happ, a switch-hitter, will likely get the most at-bats as the leadoff man. Happ batted .321 this spring, with seven home runs and 12 RBIs. The Cubs have five-time Gold Glove winner Jason Heyward in right and Kyle Schwarber in left, although he'll share that space with Zobrist. Schwarber, who batted .340 this spring, has looked good since losing weight this offseason.
Starting pitching (5): The Cubs have three Opening Day starters in their rotation in Lester, Darvish and Quintana, and Hendricks could easily have done so as well. Chatwood rounds out the starting five.
Bullpen (8): Strop is ready after missing some time because of a sore left calf and then an illness. Right-hander Brandon Morrow is the new closer, the fourth in the last four years. His setup list is long and talented, including Carl Edwards Jr., Steve Cishek, Justin Wilson, Brian Duensing, Mike Montgomery, Strop and Butler.