Defensive midfield is an area where Roberto Martinez has not had a problem with depth. With 4-5 quality players for only 1-2 starting positions, Martinez has had his pick against certain opposition. Unfortunately, injuries have ravaged the group (more than others) in the past to leave most fans thinking that there is a lack of depth.
While Tom Cleverley will mostly be called an attacking or "creative" midfielder, I think with his versatility, we can add him to this list of defensive midfielders as well. While Cleverley may not be as creative or as big of a disruptor as most fans would like, we can not deny that he is versatile enough to play most midfield and wing positions effectively.
James McCarthy: The strongest player not only in this group but one of the strongest in the whole squad, McCarthy has been included in the transfer chatter of the big spending Premier League clubs. It seems Everton are unlikely to let him leave as his importance to the club has reached peak levels. McCarthy changes the whole look of the squad. He is the master disruptor and can frustrate the best of clubs. While he is prone to some rash tackles and yellow cards, his presence is one of the most important factors if Everton would like to move up the table.
Darron Gibson: A strong player both creatively and defensively, we just haven't seen enough of him recently due to continuous injuries. While he probably won't take anyone's starting position because of his lack of playing time in the last two years, a fit Gibson will give us a starting caliber back up that could be useful late in games or in cup ties. Although Gibson is currently out , he should be back by the end of August. I will believe it when I see it.
Muhamed Bešić: Another player that has really come on strong as a disruptor, Bešić has shown flashes of brilliance. He can strike fear in opponents and show some vision. Like McCarthy, he is prone to rash tackles and yellows (and some reds as well) but is an invaluable player. Unfortunately, Bešić was injured intermittently last season and has started this year with a much feared hamstring injury.
Gareth Barry: After a very strong 2013-14 campaign, Barry's play regressed considerably. He seemed one step behind defensively throughout the pitch and lost his vision going forward as well. One of the more frustrating players last season, he is looking for a rebound in form. With a lot more competition (if the injuries all go away), we may see less of Barry this season.
Stay Healthy! We know the talent is there, it is just a case of getting fit and staying healthy for this group. Barry seems to be the only one that has had a drop off in form. Besic, McCarthy and especially Gibson need to stay away from the medical room and on the pitch in order for this position to be one of the strongest in the Everton squad. Unfortunately, only time will tell if this will happen this season.
Roberto Martinez likes to have his DMs split into a defensive and attacking mindset. Using last year's traditional pairing of McCarthy and Barry, McCarthy was the man physically getting forward more while Barry played a bit more defensively. When attacking Barry would sometimes appear to be a 3rd center back because of how deep he would drop. This would let the center backs cover the outside while the full backs went forward. Eventually Barry would also work his way into the attack when Everton was able to maintain possession. If you see Barry and McCarthy 15-20 yards from the edge of the opponent's box you know Everton is possessing extremely well at the moment.
While a strong group of defensive midfielders has gotten stronger with the addition of an offensive midfielder that can also fill in at DM, the squad needs to keep fit and stay on the field. Gareth Barry needs to find his form from two season ago, but with all the defensive midfielders fit and less playing time and wear on Barry's body, there is a greater chance of a rebound season. All we need is for Martinez to get his trainers in line!