There are 6 Cubs players who are out of options meaning they cannot be optioned to the minor leagues. They would have to be placed on waivers instead. Those players are: Michael Bowden, Welington Castillo, Rafael Dolis, Jeff Samardzija, Luis Valbuena and Travis Wood.
There are no concerns that Jeff Samardzija would need to be optioned to the minors, but that's not necessarily true of the others. The next safest player would be the Cubs starting catcher, Welington Castillo, but even he is no lock to nail down the job.
There are two reasons why Travis Wood is all but assured of being in the rotation when the season opens: he's one of the five best starters and because he's out of options. Well, he could go to the bullpen, you might say. The Cubs already have James Russell as their LOOGY and don't really need another lefty in the bullpen. Travis Wood has a lot more value in the rotation than he does in the bullpen. It doesn't hurt that he's also better than Carlos Villanueva and Scott Feldman. We already know that Feldman will be the team's 4th starter.
Although Brent Lillibridge will probably make the team out of spring training, so will Luis Valbuena. If or when the Cubs decide they need to get rid of Valbuena, it won't be a major decision and his lack of options won't be much of a factor.
The same is true for Rafael Dolis and Michael Bowden. Neither are especially good pitchers and Dolis was probaby the worst choice possible to replace Carlos Marmol as closer last season.