When Roberto Bautista-Agut began 2014, he was a relatively unknown Spanish player ranked outside the top 50 in the world. He may have a ways to go before shedding the unknown label, but he is beginning 2015 at number 15 in the world. While he wasn't a threat to win the biggest tournaments, he had an extremely successful year that seemingly came out of nowhere. Since enough attention gets placed on young stars likely to make the jump to the next level, here is a look at some players 23 or older who could pull a Roberto Bautista-Agut in 2015 and rise from outside the top 50 to inside the top 25.
Pablo Carreno Busta: Another three name Spaniard, Busta will look to make a big jump following a somewhat disappointing 2014 season. Busta garnered some attention from his breakout 2013 season, in which he seemed to win every futures and challenger level tournament he played. Based on the ranking points he gained from all his wins at the lower levels, Busta played most of 2014 on the ATP Tour. He largely struggled against the tougher competition, and failed to make much of an impact at ATP level tournaments. However, with a full year on the ATP tour under his belt, Busta should be more prepared to handle the level of competition he'll face in 2015. Lots of players struggle when they first make the move up from playing challengers, but this should all be behind Busta in 2015. He'll begin the year at 51 in the world, but look for him to finish 2015 much higher.
Federico Delbonis: Big things were expected from the Argentinean when he first started to make a name for himself on tour a few years back. He recorded a win over Roger Federer on clay in 2013, but since then hasn't produced many noteworthy results. Now 24, the big lefty should be ready to make his move after the experience he gained on tour the last few years. His best results come on clay, and Delbonis should pick up enough ranking points on the surface to make his way up the rankings.
Jan-Lennard Struff: The big hitting 24 year old German saw his ranking climb from outside the top 100 at the end of 2013 to inside the top 60 in 2014. Another rise in 2015 wouldn't be surprising, as Struff seems to be on the right track. His results were a bit spotty in 2014, and he needs to improve his consistency week in and week out. However, he plays a big game and can crack the ball off both wings. Unlike grinders whose games don't need much seasoning, Struff appears to be the type of player who will thrive from his mid-twenties on as he fully develops his game. Struff may be a bit of a wildcard, but a big jump wouldn't be overly surprising in 2015.
Donald Young: At age 25, Young may be about to enter the best stretch of his career. His failure to live up to the enormous hype has been well documented, but he did finish 2014 just outside of the top 50 in the world. He now plays like he belongs on the ATP Tour, and is still young enough to have a very productive career. He no longer has to deal with heavy expectations, as American tennis fans searching for the next big thing have moved on to the next generation. Young should have his sights set on the top 25, and his ranking has been moving in the right direction since early 2013.